| 1 | <div align="center">
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| 2 | <br>
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| 3 | <br>
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| 4 | <img src="media/logo.svg" alt="type-fest" height="300">
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| 5 | <br>
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| 6 | <br>
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| 7 | <b>A collection of essential TypeScript types</b>
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| 8 | <br>
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| 9 | <hr>
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| 10 | </div>
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| 11 | <br>
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| 12 | <br>
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| 13 |
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| 14 | [](https://giphy.com/gifs/illustration-rainbow-unicorn-26AHG5KGFxSkUWw1i)
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| 15 | <!-- Commented out until they actually show anything
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| 16 | [](https://www.npmjs.com/package/type-fest?activeTab=dependents) [](https://www.npmjs.com/package/type-fest)
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| 17 | -->
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| 18 |
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| 19 | Many of the types here should have been built-in. You can help by suggesting some of them to the [TypeScript project](https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md).
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| 20 |
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| 21 | Either add this package as a dependency or copy-paste the needed types. No credit required. 👌
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| 22 |
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| 23 | PR welcome for additional commonly needed types and docs improvements. Read the [contributing guidelines](.github/contributing.md) first.
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| 24 |
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| 25 | ## Install
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| 26 |
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| 27 | ```
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| 28 | $ npm install type-fest
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| 29 | ```
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| 30 |
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| 31 | *Requires TypeScript >=3.4*
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| 32 |
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| 33 | ## Usage
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| 34 |
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| 35 | ```ts
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| 36 | import {Except} from 'type-fest';
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| 37 |
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| 38 | type Foo = {
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| 39 | unicorn: string;
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| 40 | rainbow: boolean;
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| 41 | };
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| 42 |
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| 43 | type FooWithoutRainbow = Except<Foo, 'rainbow'>;
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| 44 | //=> {unicorn: string}
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| 45 | ```
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| 46 |
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| 47 | ## API
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| 48 |
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| 49 | Click the type names for complete docs.
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| 50 |
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| 51 | ### Basic
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| 52 |
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| 53 | - [`Primitive`](source/basic.d.ts) - Matches any [primitive value](https://developer.mozilla.org/en-US/docs/Glossary/Primitive).
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| 54 | - [`Class`](source/basic.d.ts) - Matches a [`class` constructor](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes).
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| 55 | - [`TypedArray`](source/basic.d.ts) - Matches any [typed array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray), like `Uint8Array` or `Float64Array`.
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| 56 | - [`JsonObject`](source/basic.d.ts) - Matches a JSON object.
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| 57 | - [`JsonArray`](source/basic.d.ts) - Matches a JSON array.
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| 58 | - [`JsonValue`](source/basic.d.ts) - Matches any valid JSON value.
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| 59 | - [`ObservableLike`](source/basic.d.ts) - Matches a value that is like an [Observable](https://github.com/tc39/proposal-observable).
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| 60 |
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| 61 | ### Utilities
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| 62 |
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| 63 | - [`Except`](source/except.d.ts) - Create a type from an object type without certain keys. This is a stricter version of [`Omit`](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-5.html#the-omit-helper-type).
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| 64 | - [`Mutable`](source/mutable.d.ts) - Convert an object with `readonly` keys into a mutable object. The inverse of `Readonly<T>`.
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| 65 | - [`Merge`](source/merge.d.ts) - Merge two types into a new type. Keys of the second type overrides keys of the first type.
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| 66 | - [`MergeExclusive`](source/merge-exclusive.d.ts) - Create a type that has mutually exclusive keys.
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| 67 | - [`RequireAtLeastOne`](source/require-at-least-one.d.ts) - Create a type that requires at least one of the given keys.
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| 68 | - [`RequireExactlyOne`](source/require-exactly-one.d.ts) - Create a type that requires exactly a single key of the given keys and disallows more.
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| 69 | - [`PartialDeep`](source/partial-deep.d.ts) - Create a deeply optional version of another type. Use [`Partial<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1401-L1406) if you only need one level deep.
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| 70 | - [`ReadonlyDeep`](source/readonly-deep.d.ts) - Create a deeply immutable version of an `object`/`Map`/`Set`/`Array` type. Use [`Readonly<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1415-L1420) if you only need one level deep.
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| 71 | - [`LiteralUnion`](source/literal-union.d.ts) - Create a union type by combining primitive types and literal types without sacrificing auto-completion in IDEs for the literal type part of the union. Workaround for [Microsoft/TypeScript#29729](https://github.com/Microsoft/TypeScript/issues/29729).
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| 72 | - [`Promisable`](source/promisable.d.ts) - Create a type that represents either the value or the value wrapped in `PromiseLike`.
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| 73 | - [`Opaque`](source/opaque.d.ts) - Create an [opaque type](https://codemix.com/opaque-types-in-javascript/).
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| 74 | - [`SetOptional`](source/set-optional.d.ts) - Create a type that makes the given keys optional.
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| 75 | - [`SetRequired`](source/set-required.d.ts) - Create a type that makes the given keys required.
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| 76 | - [`ValueOf`](source/value-of.d.ts) - Create a union of the given object's values, and optionally specify which keys to get the values from.
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| 77 | - [`PromiseValue`](source/promise-value.d.ts) - Returns the type that is wrapped inside a `Promise`.
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| 78 | - [`AsyncReturnType`](source/async-return-type.d.ts) - Unwrap the return type of a function that returns a `Promise`.
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| 79 | - [`ConditionalKeys`](source/conditional-keys.d.ts) - Extract keys from a shape where values extend the given `Condition` type.
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| 80 | - [`ConditionalPick`](source/conditional-pick.d.ts) - Like `Pick` except it selects properties from a shape where the values extend the given `Condition` type.
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| 81 | - [`ConditionalExcept`](source/conditional-except.d.ts) - Like `Omit` except it removes properties from a shape where the values extend the given `Condition` type.
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| 82 | - [`UnionToIntersection`](source/union-to-intersection.d.ts) - Convert a union type to an intersection type.
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| 83 | - [`Stringified`](source/stringified.d.ts) - Create a type with the keys of the given type changed to `string` type.
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| 84 | - [`FixedLengthArray`](source/fixed-length-array.d.ts) - Create a type that represents an array of the given type and length.
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| 85 | - [`IterableElement`](source/iterable-element.d.ts) - Get the element type of an `Iterable`/`AsyncIterable`. For example, an array or a generator.
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| 86 | - [`Entry`](source/entry.d.ts) - Create a type that represents the type of an entry of a collection.
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| 87 | - [`Entries`](source/entries.d.ts) - Create a type that represents the type of the entries of a collection.
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| 88 | - [`SetReturnType`](source/set-return-type.d.ts) - Create a function type with a return type of your choice and the same parameters as the given function type.
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| 89 | - [`Asyncify`](source/asyncify.d.ts) - Create an async version of the given function type.
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| 90 |
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| 91 | ### Template literal types
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| 92 |
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| 93 | *Note:* These require [TypeScript 4.1 or newer](https://devblogs.microsoft.com/typescript/announcing-typescript-4-1/#template-literal-types).
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| 94 |
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| 95 | - [`CamelCase`](ts41/camel-case.d.ts) – Convert a string literal to camel-case (`fooBar`).
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| 96 | - [`KebabCase`](ts41/kebab-case.d.ts) – Convert a string literal to kebab-case (`foo-bar`).
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| 97 | - [`PascalCase`](ts41/pascal-case.d.ts) – Converts a string literal to pascal-case (`FooBar`)
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| 98 | - [`SnakeCase`](ts41/snake-case.d.ts) – Convert a string literal to snake-case (`foo_bar`).
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| 99 | - [`DelimiterCase`](ts41/delimiter-case.d.ts) – Convert a string literal to a custom string delimiter casing.
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| 100 |
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| 101 | ### Miscellaneous
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| 102 |
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| 103 | - [`PackageJson`](source/package-json.d.ts) - Type for [npm's `package.json` file](https://docs.npmjs.com/creating-a-package-json-file).
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| 104 | - [`TsConfigJson`](source/tsconfig-json.d.ts) - Type for [TypeScript's `tsconfig.json` file](https://www.typescriptlang.org/docs/handbook/tsconfig-json.html) (TypeScript 3.7).
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| 105 |
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| 106 | ## Declined types
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| 107 |
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| 108 | *If we decline a type addition, we will make sure to document the better solution here.*
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| 109 |
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| 110 | - [`Diff` and `Spread`](https://github.com/sindresorhus/type-fest/pull/7) - The PR author didn't provide any real-world use-cases and the PR went stale. If you think this type is useful, provide some real-world use-cases and we might reconsider.
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| 111 | - [`Dictionary`](https://github.com/sindresorhus/type-fest/issues/33) - You only save a few characters (`Dictionary<number>` vs `Record<string, number>`) from [`Record`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1429-L1434), which is more flexible and well-known. Also, you shouldn't use an object as a dictionary. We have `Map` in JavaScript now.
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| 112 | - [`SubType`](https://github.com/sindresorhus/type-fest/issues/22) - The type is powerful, but lacks good use-cases and is prone to misuse.
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| 113 | - [`ExtractProperties` and `ExtractMethods`](https://github.com/sindresorhus/type-fest/pull/4) - The types violate the single responsibility principle. Instead, refine your types into more granular type hierarchies.
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| 114 |
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| 115 | ## Tips
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| 116 |
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| 117 | ### Built-in types
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| 118 |
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| 119 | There are many advanced types most users don't know about.
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| 120 |
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| 121 | - [`Partial<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1401-L1406) - Make all properties in `T` optional.
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| 122 | <details>
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| 123 | <summary>
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| 124 | Example
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| 125 | </summary>
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| 126 |
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| 127 | [Playground](https://www.typescriptlang.org/play/#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)
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| 128 |
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| 129 | ```ts
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| 130 | interface NodeConfig {
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| 131 | appName: string;
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| 132 | port: number;
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| 133 | }
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| 134 |
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| 135 | class NodeAppBuilder {
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| 136 | private configuration: NodeConfig = {
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| 137 | appName: 'NodeApp',
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| 138 | port: 3000
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| 139 | };
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| 140 |
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| 141 | private updateConfig<Key extends keyof NodeConfig>(key: Key, value: NodeConfig[Key]) {
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| 142 | this.configuration[key] = value;
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| 143 | }
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| 144 |
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| 145 | config(config: Partial<NodeConfig>) {
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| 146 | type NodeConfigKey = keyof NodeConfig;
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| 147 |
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| 148 | for (const key of Object.keys(config) as NodeConfigKey[]) {
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| 149 | const updateValue = config[key];
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| 150 |
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| 151 | if (updateValue === undefined) {
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| 152 | continue;
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| 153 | }
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| 154 |
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| 155 | this.updateConfig(key, updateValue);
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| 156 | }
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| 157 |
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| 158 | return this;
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| 159 | }
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| 160 | }
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| 161 |
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| 162 | // `Partial<NodeConfig>`` allows us to provide only a part of the
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| 163 | // NodeConfig interface.
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| 164 | new NodeAppBuilder().config({appName: 'ToDoApp'});
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| 165 | ```
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| 166 | </details>
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| 167 |
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| 168 | - [`Required<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1408-L1413) - Make all properties in `T` required.
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| 169 | <details>
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| 170 | <summary>
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| 171 | Example
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| 172 | </summary>
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| 173 |
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| 174 | [Playground](https://typescript-play.js.org/?target=6#code/AQ4SwOwFwUwJwGYEMDGNgGED21VQGJZwC2wA3gFCjXAzFJgA2A-AFzADOUckA5gNxUaIYjA4ckvGG07c+g6gF8KQkAgCuEFFDA5O6gEbEwUbLm2ESwABQIixACJIoSdgCUYAR3Vg4MACYAPGYuFvYAfACU5Ko0APRxwADKMBD+wFAAFuh2Vv7OSBlYGdmc8ABu8LHKsRyGxqY4oQT21pTCIHQMjOwA5DAAHgACxAAOjDAAdChYxL0ANLHUouKSMH0AEmAAhJhY6ozpAJ77GTCMjMCiV0ToSAb7UJPPC9WRgrEJwAAqR6MwSRQPFGUFocDgRHYxnEfGAowh-zgUCOwF6KwkUl6tXqJhCeEsxDaS1AXSYfUGI3GUxmc0WSneQA)
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| 175 |
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| 176 | ```ts
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| 177 | interface ContactForm {
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| 178 | email?: string;
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| 179 | message?: string;
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| 180 | }
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| 181 |
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| 182 | function submitContactForm(formData: Required<ContactForm>) {
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| 183 | // Send the form data to the server.
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| 184 | }
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| 185 |
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| 186 | submitContactForm({
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| 187 | email: 'ex@mple.com',
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| 188 | message: 'Hi! Could you tell me more about…',
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| 189 | });
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| 190 |
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| 191 | // TypeScript error: missing property 'message'
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| 192 | submitContactForm({
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| 193 | email: 'ex@mple.com',
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| 194 | });
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| 195 | ```
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| 196 | </details>
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| 197 |
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| 198 | - [`Readonly<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1415-L1420) - Make all properties in `T` readonly.
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| 199 | <details>
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| 200 | <summary>
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| 201 | Example
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| 202 | </summary>
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| 203 |
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| 204 | [Playground](https://typescript-play.js.org/?target=6#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)
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| 205 |
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| 206 | ```ts
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| 207 | enum LogLevel {
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| 208 | Off,
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| 209 | Debug,
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| 210 | Error,
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| 211 | Fatal
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| 212 | };
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| 213 |
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| 214 | interface LoggerConfig {
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| 215 | name: string;
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| 216 | level: LogLevel;
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| 217 | }
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| 218 |
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| 219 | class Logger {
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| 220 | config: Readonly<LoggerConfig>;
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| 221 |
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| 222 | constructor({name, level}: LoggerConfig) {
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| 223 | this.config = {name, level};
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| 224 | Object.freeze(this.config);
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| 225 | }
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| 226 | }
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| 227 |
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| 228 | const config: LoggerConfig = {
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| 229 | name: 'MyApp',
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| 230 | level: LogLevel.Debug
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| 231 | };
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| 232 |
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| 233 | const logger = new Logger(config);
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| 234 |
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| 235 | // TypeScript Error: cannot assign to read-only property.
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| 236 | logger.config.level = LogLevel.Error;
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| 237 |
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| 238 | // We are able to edit config variable as we please.
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| 239 | config.level = LogLevel.Error;
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| 240 | ```
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| 241 | </details>
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| 242 |
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| 243 | - [`Pick<T, K>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1422-L1427) - From `T`, pick a set of properties whose keys are in the union `K`.
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| 244 | <details>
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| 245 | <summary>
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| 246 | Example
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| 247 | </summary>
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| 248 |
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| 249 | [Playground](https://typescript-play.js.org/?target=6#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)
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| 250 |
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| 251 | ```ts
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| 252 | interface Article {
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| 253 | title: string;
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| 254 | thumbnail: string;
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| 255 | content: string;
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| 256 | }
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| 257 |
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| 258 | // Creates new type out of the `Article` interface composed
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| 259 | // from the Articles' two properties: `title` and `thumbnail`.
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| 260 | // `ArticlePreview = {title: string; thumbnail: string}`
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| 261 | type ArticlePreview = Pick<Article, 'title' | 'thumbnail'>;
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| 262 |
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| 263 | // Render a list of articles using only title and description.
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| 264 | function renderArticlePreviews(previews: ArticlePreview[]): HTMLElement {
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| 265 | const articles = document.createElement('div');
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| 266 |
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| 267 | for (const preview of previews) {
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| 268 | // Append preview to the articles.
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| 269 | }
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| 270 |
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| 271 | return articles;
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| 272 | }
|
|---|
| 273 |
|
|---|
| 274 | const articles = renderArticlePreviews([
|
|---|
| 275 | {
|
|---|
| 276 | title: 'TypeScript tutorial!',
|
|---|
| 277 | thumbnail: '/assets/ts.jpg'
|
|---|
| 278 | }
|
|---|
| 279 | ]);
|
|---|
| 280 | ```
|
|---|
| 281 | </details>
|
|---|
| 282 |
|
|---|
| 283 | - [`Record<K, T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1429-L1434) - Construct a type with a set of properties `K` of type `T`.
|
|---|
| 284 | <details>
|
|---|
| 285 | <summary>
|
|---|
| 286 | Example
|
|---|
| 287 | </summary>
|
|---|
| 288 |
|
|---|
| 289 | [Playground](https://typescript-play.js.org/?target=6#code/AQ4ejYAUHsGcCWAXBMB2dgwGbAKYC2ADgDYwCeeemCaWArgE7ADGMxAhmuQHQBQoYEnJE8wALKEARnkaxEKdMAC8wAOS0kstGuAAfdQBM8ANzxlRjXQbVaWACwC0JPB0NqA3HwGgIwAJJoWozYHCxixnAsjAhStADmwESMMJYo1Fi4HMCIaPEu+MRklHj8gpqyoeHAAKJFFFTAAN4+giDYCIxwSAByHAR4AFw5SDF5Xm2gJBzdfQPD3WPxE5PAlBxdAPLYNQAelgh4aOHDaPQEMowrIAC+3oJ+AMKMrlrAXFhSAFZ4LEhC9g4-0BmA4JBISXgiCkBQABpILrJ5MhUGhYcATGD6Bk4Hh-jNgABrPDkOBlXyQAAq9ngYmJpOAAHcEOCRjAXqwYODfoo6DhakUSph+Uh7GI4P0xER4Cj0OSQGwMP8tP1hgAlX7swwAHgRl2RvIANALSA08ABtAC6AD4VM1Wm0Kow0MMrYaHYJjGYLLJXZb3at1HYnC43Go-QHQDcvA6-JsmEJXARgCDgMYWAhjIYhDAU+YiMAAFIwex0ZmilMITCGF79TLAGRsAgJYAAZRwSEZGzEABFTOZUrJ5Yn+jwnWgeER6HB7AAKJrADpdXqS4ZqYultTG6azVfqHswPBbtauLY7fayQ7HIbAAAMwBuAEoYw9IBq2Ixs9h2eFMOQYPQObALQKJgggABeYhghCIpikkKRpOQRIknAsZUiIeCttECBEP8NSMCkjDDAARMGziuIYxHwYOjDCMBmDNnAuTxA6irdCOBB1Lh5Dqpqn66tISIykawBnOCtqqC0gbjqc9DgpGkxegOliyfJDrRkAA)
|
|---|
| 290 |
|
|---|
| 291 | ```ts
|
|---|
| 292 | // Positions of employees in our company.
|
|---|
| 293 | type MemberPosition = 'intern' | 'developer' | 'tech-lead';
|
|---|
| 294 |
|
|---|
| 295 | // Interface describing properties of a single employee.
|
|---|
| 296 | interface Employee {
|
|---|
| 297 | firstName: string;
|
|---|
| 298 | lastName: string;
|
|---|
| 299 | yearsOfExperience: number;
|
|---|
| 300 | }
|
|---|
| 301 |
|
|---|
| 302 | // Create an object that has all possible `MemberPosition` values set as keys.
|
|---|
| 303 | // Those keys will store a collection of Employees of the same position.
|
|---|
| 304 | const team: Record<MemberPosition, Employee[]> = {
|
|---|
| 305 | intern: [],
|
|---|
| 306 | developer: [],
|
|---|
| 307 | 'tech-lead': [],
|
|---|
| 308 | };
|
|---|
| 309 |
|
|---|
| 310 | // Our team has decided to help John with his dream of becoming Software Developer.
|
|---|
| 311 | team.intern.push({
|
|---|
| 312 | firstName: 'John',
|
|---|
| 313 | lastName: 'Doe',
|
|---|
| 314 | yearsOfExperience: 0
|
|---|
| 315 | });
|
|---|
| 316 |
|
|---|
| 317 | // `Record` forces you to initialize all of the property keys.
|
|---|
| 318 | // TypeScript Error: "tech-lead" property is missing
|
|---|
| 319 | const teamEmpty: Record<MemberPosition, null> = {
|
|---|
| 320 | intern: null,
|
|---|
| 321 | developer: null,
|
|---|
| 322 | };
|
|---|
| 323 | ```
|
|---|
| 324 | </details>
|
|---|
| 325 |
|
|---|
| 326 | - [`Exclude<T, U>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1436-L1439) - Exclude from `T` those types that are assignable to `U`.
|
|---|
| 327 | <details>
|
|---|
| 328 | <summary>
|
|---|
| 329 | Example
|
|---|
| 330 | </summary>
|
|---|
| 331 |
|
|---|
| 332 | [Playground](https://typescript-play.js.org/?target=6#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)
|
|---|
| 333 |
|
|---|
| 334 | ```ts
|
|---|
| 335 | interface ServerConfig {
|
|---|
| 336 | port: null | string | number;
|
|---|
| 337 | }
|
|---|
| 338 |
|
|---|
| 339 | type RequestHandler = (request: Request, response: Response) => void;
|
|---|
| 340 |
|
|---|
| 341 | // Exclude `null` type from `null | string | number`.
|
|---|
| 342 | // In case the port is equal to `null`, we will use default value.
|
|---|
| 343 | function getPortValue(port: Exclude<ServerConfig['port'], null>): number {
|
|---|
| 344 | if (typeof port === 'string') {
|
|---|
| 345 | return parseInt(port, 10);
|
|---|
| 346 | }
|
|---|
| 347 |
|
|---|
| 348 | return port;
|
|---|
| 349 | }
|
|---|
| 350 |
|
|---|
| 351 | function startServer(handler: RequestHandler, config: ServerConfig): void {
|
|---|
| 352 | const server = require('http').createServer(handler);
|
|---|
| 353 |
|
|---|
| 354 | const port = config.port === null ? 3000 : getPortValue(config.port);
|
|---|
| 355 | server.listen(port);
|
|---|
| 356 | }
|
|---|
| 357 | ```
|
|---|
| 358 | </details>
|
|---|
| 359 |
|
|---|
| 360 | - [`Extract<T, U>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1441-L1444) - Extract from `T` those types that are assignable to `U`.
|
|---|
| 361 | <details>
|
|---|
| 362 | <summary>
|
|---|
| 363 | Example
|
|---|
| 364 | </summary>
|
|---|
| 365 |
|
|---|
| 366 | [Playground](https://typescript-play.js.org/?target=6#code/CYUwxgNghgTiAEAzArgOzAFwJYHtXzSwEdkQBJYACgEoAueVZAWwCMQYBuAKDDwGcM8MgBF4AXngBlAJ6scESgHIRi6ty5ZUGdoihgEABXZ888AN5d48ANoiAuvUat23K6ihMQ9ATE0BzV3goPy8GZjZOLgBfLi4Aejj4AEEICBwAdz54MAALKFQQ+BxEeAAHY1NgKAwoIKy0grr4DByEUpgccpgMaXgAaxBerCzi+B9-ZulygDouFHRsU1z8kKMYE1RhaqgAHkt4AHkWACt4EAAPbVRgLLWNgBp9gGlBs8uQa6yAUUuYPQwdgNpKM7nh7mMML4CgA+R5WABqUAgpDeVxuhxO1he0jsXGh8EoOBO9COx3BQPo2PBADckaR6IjkSA6PBqTgsMBzPsicdrEC7OJWXSQNwYvFEgAVTS9JLXODpeDpKBZFg4GCoWa8VACIJykAKiQWKy2YQOAioYikCg0OEMDyhRSy4DyxS24KhAAMjyi6gS8AAwjh5OD0iBFHAkJoEOksC1mnkMJq8gUQKDNttKPlnfrwYp3J5XfBHXqoKpfYkAOI4ansTxaeDADmoRSCCBYAbxhC6TDx6rwYHIRX5bScjA4bLJwoDmDwDkfbA9JMrVMVdM1TN69LgkTgwgkchUahqIA)
|
|---|
| 367 |
|
|---|
| 368 | ```ts
|
|---|
| 369 | declare function uniqueId(): number;
|
|---|
| 370 |
|
|---|
| 371 | const ID = Symbol('ID');
|
|---|
| 372 |
|
|---|
| 373 | interface Person {
|
|---|
| 374 | [ID]: number;
|
|---|
| 375 | name: string;
|
|---|
| 376 | age: number;
|
|---|
| 377 | }
|
|---|
| 378 |
|
|---|
| 379 | // Allows changing the person data as long as the property key is of string type.
|
|---|
| 380 | function changePersonData<
|
|---|
| 381 | Obj extends Person,
|
|---|
| 382 | Key extends Extract<keyof Person, string>,
|
|---|
| 383 | Value extends Obj[Key]
|
|---|
| 384 | > (obj: Obj, key: Key, value: Value): void {
|
|---|
| 385 | obj[key] = value;
|
|---|
| 386 | }
|
|---|
| 387 |
|
|---|
| 388 | // Tiny Andrew was born.
|
|---|
| 389 | const andrew = {
|
|---|
| 390 | [ID]: uniqueId(),
|
|---|
| 391 | name: 'Andrew',
|
|---|
| 392 | age: 0,
|
|---|
| 393 | };
|
|---|
| 394 |
|
|---|
| 395 | // Cool, we're fine with that.
|
|---|
| 396 | changePersonData(andrew, 'name', 'Pony');
|
|---|
| 397 |
|
|---|
| 398 | // Goverment didn't like the fact that you wanted to change your identity.
|
|---|
| 399 | changePersonData(andrew, ID, uniqueId());
|
|---|
| 400 | ```
|
|---|
| 401 | </details>
|
|---|
| 402 |
|
|---|
| 403 | - [`NonNullable<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1446-L1449) - Exclude `null` and `undefined` from `T`.
|
|---|
| 404 | <details>
|
|---|
| 405 | <summary>
|
|---|
| 406 | Example
|
|---|
| 407 | </summary>
|
|---|
| 408 | Works with <code>strictNullChecks</code> set to <code>true</code>. (Read more <a href="https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-0.html">here</a>)
|
|---|
| 409 |
|
|---|
| 410 | [Playground](https://typescript-play.js.org/?target=6#code/C4TwDgpgBACg9gJ2AOQK4FsBGEFQLxQDOwCAlgHYDmUAPlORtrnQwDasDcAUFwPQBU-WAEMkUOADMowqAGNWwwoSgATCBIqlgpOOSjAAFsOBRSy1IQgr9cKJlSlW1mZYQA3HFH68u8xcoBlHA8EACEHJ08Aby4oKDBUTFZSWXjEFEYcAEIALihkXTR2YSSIAB54JDQsHAA+blj4xOTUsHSACkMzPKD3HHDHNQQAGjSkPMqMmoQASh7g-oihqBi4uNIpdraxPAI2VhmVxrX9AzMAOm2ppnwoAA4ABifuE4BfKAhWSyOTuK7CS7pao3AhXF5rV48E4ICDAVAIPT-cGQyG+XTEIgLMJLTx7CAAdygvRCA0iCHaMwarhJOIQjUBSHaACJHk8mYdeLwxtdcVAAOSsh58+lXdr7Dlcq7A3n3J4PEUdADMcspUE53OluAIUGVTx46oAKuAIAFZGQwCYAKIIBCILjUxaDHAMnla+iodjcIA)
|
|---|
| 411 |
|
|---|
| 412 | ```ts
|
|---|
| 413 | type PortNumber = string | number | null;
|
|---|
| 414 |
|
|---|
| 415 | /** Part of a class definition that is used to build a server */
|
|---|
| 416 | class ServerBuilder {
|
|---|
| 417 | portNumber!: NonNullable<PortNumber>;
|
|---|
| 418 |
|
|---|
| 419 | port(this: ServerBuilder, port: PortNumber): ServerBuilder {
|
|---|
| 420 | if (port == null) {
|
|---|
| 421 | this.portNumber = 8000;
|
|---|
| 422 | } else {
|
|---|
| 423 | this.portNumber = port;
|
|---|
| 424 | }
|
|---|
| 425 |
|
|---|
| 426 | return this;
|
|---|
| 427 | }
|
|---|
| 428 | }
|
|---|
| 429 |
|
|---|
| 430 | const serverBuilder = new ServerBuilder();
|
|---|
| 431 |
|
|---|
| 432 | serverBuilder
|
|---|
| 433 | .port('8000') // portNumber = '8000'
|
|---|
| 434 | .port(null) // portNumber = 8000
|
|---|
| 435 | .port(3000); // portNumber = 3000
|
|---|
| 436 |
|
|---|
| 437 | // TypeScript error
|
|---|
| 438 | serverBuilder.portNumber = null;
|
|---|
| 439 | ```
|
|---|
| 440 | </details>
|
|---|
| 441 |
|
|---|
| 442 | - [`Parameters<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1451-L1454) - Obtain the parameters of a function type in a tuple.
|
|---|
| 443 | <details>
|
|---|
| 444 | <summary>
|
|---|
| 445 | Example
|
|---|
| 446 | </summary>
|
|---|
| 447 |
|
|---|
| 448 | [Playground](https://typescript-play.js.org/?target=6#code/GYVwdgxgLglg9mABAZwBYmMANgUwBQxgAOIUAXIgIZgCeA2gLoCUFAbnDACaIDeAUIkQB6IYgCypSlBxUATrMo1ECsJzgBbLEoipqAc0J7EMKMgDkiHLnU4wp46pwAPHMgB0fAL58+oSLARECEosLAA5ABUYG2QAHgAxJGdpVWREPDdMylk9ZApqemZEAF4APipacrw-CApEgBogkKwAYThwckQwEHUAIxxZJl4BYVEImiIZKF0oZRwiWVdbeygJmThgOYgcGFYcbhqApCJsyhtpWXcR1cnEePBoeDAABVPzgbTixFeFd8uEsClADcIxGiygIFkSEOT3SmTc2VydQeRx+ZxwF2QQ34gkEwDgsnSuFmMBKiAADEDjIhYk1Qm0OlSYABqZnYka4xA1DJZHJYkGc7yCbyeRA+CAIZCzNAYbA4CIAdxg2zJwVCkWirjwMswuEaACYmCCgA)
|
|---|
| 449 |
|
|---|
| 450 | ```ts
|
|---|
| 451 | function shuffle(input: any[]): void {
|
|---|
| 452 | // Mutate array randomly changing its' elements indexes.
|
|---|
| 453 | }
|
|---|
| 454 |
|
|---|
| 455 | function callNTimes<Fn extends (...args: any[]) => any> (func: Fn, callCount: number) {
|
|---|
| 456 | // Type that represents the type of the received function parameters.
|
|---|
| 457 | type FunctionParameters = Parameters<Fn>;
|
|---|
| 458 |
|
|---|
| 459 | return function (...args: FunctionParameters) {
|
|---|
| 460 | for (let i = 0; i < callCount; i++) {
|
|---|
| 461 | func(...args);
|
|---|
| 462 | }
|
|---|
| 463 | }
|
|---|
| 464 | }
|
|---|
| 465 |
|
|---|
| 466 | const shuffleTwice = callNTimes(shuffle, 2);
|
|---|
| 467 | ```
|
|---|
| 468 | </details>
|
|---|
| 469 |
|
|---|
| 470 | - [`ConstructorParameters<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1456-L1459) - Obtain the parameters of a constructor function type in a tuple.
|
|---|
| 471 | <details>
|
|---|
| 472 | <summary>
|
|---|
| 473 | Example
|
|---|
| 474 | </summary>
|
|---|
| 475 |
|
|---|
| 476 | [Playground](https://typescript-play.js.org/?target=6#code/MYGwhgzhAECCBOAXAlqApgWQPYBM0mgG8AoaaFRENALmgkXmQDsBzAblOmCycTV4D8teo1YdO3JiICuwRFngAKClWENmLAJRFOZRAAtkEAHQq00ALzlklNBzIBfYk+KhIMAJJTEYJsDQAwmDA+mgAPAAq0GgAHnxMODCKTGgA7tCKxllg8CwQtL4AngDaALraFgB80EWa1SRkAA6MAG5gfNAB4FABPDJyCrQR9tDNyG0dwMGhtBhgjWEiGgA00F70vv4RhY3hEZXVVinpc42KmuJkkv3y8Bly8EPaDWTkhiZd7r3e8LK3llwGCMXGQWGhEOsfH5zJlsrl8p0+gw-goAAo5MAAW3BaHgEEilU0tEhmzQ212BJ0ry4SOg+kg+gBBiMximIGA0nAfAQLGk2N4EAAEgzYcYcnkLsRdDTvNEYkYUKwSdCme9WdM0MYwYhFPSIPpJdTkAAzDKxBUaZX+aAAQgsVmkCTQxuYaBw2ng4Ok8CYcotSu8pMur09iG9vuObxZnx6SN+AyUWTF8MN0CcZE4Ywm5jZHK5aB5fP4iCFIqT4oRRTKRLo6lYVNeAHpG50wOzOe1zHr9NLQ+HoABybsD4HOKXXRA1JCoKhBELmI5pNaB6Fz0KKBAodDYPAgSUTmqYsAALx4m5nC6nW9nGq14KtaEUA9gR9PvuNCjQ9BgACNvcwNBtAcLiAA)
|
|---|
| 477 |
|
|---|
| 478 | ```ts
|
|---|
| 479 | class ArticleModel {
|
|---|
| 480 | title: string;
|
|---|
| 481 | content?: string;
|
|---|
| 482 |
|
|---|
| 483 | constructor(title: string) {
|
|---|
| 484 | this.title = title;
|
|---|
| 485 | }
|
|---|
| 486 | }
|
|---|
| 487 |
|
|---|
| 488 | class InstanceCache<T extends (new (...args: any[]) => any)> {
|
|---|
| 489 | private ClassConstructor: T;
|
|---|
| 490 | private cache: Map<string, InstanceType<T>> = new Map();
|
|---|
| 491 |
|
|---|
| 492 | constructor (ctr: T) {
|
|---|
| 493 | this.ClassConstructor = ctr;
|
|---|
| 494 | }
|
|---|
| 495 |
|
|---|
| 496 | getInstance (...args: ConstructorParameters<T>): InstanceType<T> {
|
|---|
| 497 | const hash = this.calculateArgumentsHash(...args);
|
|---|
| 498 |
|
|---|
| 499 | const existingInstance = this.cache.get(hash);
|
|---|
| 500 | if (existingInstance !== undefined) {
|
|---|
| 501 | return existingInstance;
|
|---|
| 502 | }
|
|---|
| 503 |
|
|---|
| 504 | return new this.ClassConstructor(...args);
|
|---|
| 505 | }
|
|---|
| 506 |
|
|---|
| 507 | private calculateArgumentsHash(...args: any[]): string {
|
|---|
| 508 | // Calculate hash.
|
|---|
| 509 | return 'hash';
|
|---|
| 510 | }
|
|---|
| 511 | }
|
|---|
| 512 |
|
|---|
| 513 | const articleCache = new InstanceCache(ArticleModel);
|
|---|
| 514 | const amazonArticle = articleCache.getInstance('Amazon forests burining!');
|
|---|
| 515 | ```
|
|---|
| 516 | </details>
|
|---|
| 517 |
|
|---|
| 518 | - [`ReturnType<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1461-L1464) – Obtain the return type of a function type.
|
|---|
| 519 | <details>
|
|---|
| 520 | <summary>
|
|---|
| 521 | Example
|
|---|
| 522 | </summary>
|
|---|
| 523 |
|
|---|
| 524 | [Playground](https://typescript-play.js.org/?target=6#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-YhAA+qegAAYLKQLQj3ZsEsdccmnGcLor2Dn8xGedHGpEIBzEzspfsfMHDNAANTQACMVaIljV5GQkRA5DYmIpVKQAgAJARO9le33BDXIyi0YuLW2nJFGLqkOvxFB0YPdBSaLZ0IwNzyPkO8-xkGgsLh8Al427a3hWAhXwwHA8EHT5PmgAB1bAQBAANJ24adKWpft72RaBUTgRBUCAj89HAM8xCTaBjggABRQx0DuHJv25P9dCkWRZVIAAiBjoFImpmjlFBgA0NpsjadByDacgIDAEAIAAQmYpjoGYgAZSBsmGPw6DtZiiFA8CoJguDmAQmoZ2QvtUKQLdoAYmBTwgdEiCAA)
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| 525 |
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| 526 | ```ts
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| 527 | /** Provides every element of the iterable `iter` into the `callback` function and stores the results in an array. */
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| 528 | function mapIter<
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| 529 | Elem,
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| 530 | Func extends (elem: Elem) => any,
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| 531 | Ret extends ReturnType<Func>
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| 532 | >(iter: Iterable<Elem>, callback: Func): Ret[] {
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| 533 | const mapped: Ret[] = [];
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| 534 |
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| 535 | for (const elem of iter) {
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| 536 | mapped.push(callback(elem));
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| 537 | }
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| 538 |
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| 539 | return mapped;
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| 540 | }
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| 541 |
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| 542 | const setObject: Set<string> = new Set();
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| 543 | const mapObject: Map<number, string> = new Map();
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| 544 |
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| 545 | mapIter(setObject, (value: string) => value.indexOf('Foo')); // number[]
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| 546 |
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| 547 | mapIter(mapObject, ([key, value]: [number, string]) => {
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| 548 | return key % 2 === 0 ? value : 'Odd';
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| 549 | }); // string[]
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| 550 | ```
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| 551 | </details>
|
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| 552 |
|
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| 553 | - [`InstanceType<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1466-L1469) – Obtain the instance type of a constructor function type.
|
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| 554 | <details>
|
|---|
| 555 | <summary>
|
|---|
| 556 | Example
|
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| 557 | </summary>
|
|---|
| 558 |
|
|---|
| 559 | [Playground](https://typescript-play.js.org/?target=6#code/MYGwhgzhAECSAmICmBlJAnAbgS2E6A3gFDTTwD2AcuQC4AW2AdgOYAUAlAFzSbnbyEAvkWFFQkGJSQB3GMVI1sNZNwg10TZgG4S0YOUY0kh1es07d+xmvQBXYDXLpWi5UlMaWAGj0GjJ6BtNdkJdBQYIADpXZGgAXmgYpB1ScOwoq38aeN9DYxoU6GFRKzVoJjUwRjwAYXJbPPRuAFkwAAcAHgAxBodsAx9GWwBbACMMAD4cxhloVraOCyYjdAAzMDxoOut1e0d0UNIZ6WhWSPOwdGYIbiqATwBtAF0uaHudUQB6ACpv6ABpJBINqJdAbADW0Do5BOw3u5R2VTwMHIq2gAANtjZ0bkbHsnFCwJh8ONjHp0EgwEZ4JFoN9PkRVr1FAZoMwkDRYIjqkgOrosepoEgAB7+eAwAV2BxOLy6ACCVxgIrFEoMeOl6AACpcwMMORgIB1JRMiBNWKVdhruJKfOdIpdrtwFddXlzKjyACp3Nq842HaDIbL6BrZBIVGhIpB1EMYSLsmjmtWW-YhAA+qegAAYLKQLQj3ZsEsdccmnGcLor2Dn8xGedHGpEIBzEzspfsfMHDNAANTQACMVaIljV5GQkRA5DYmIpVKQAgAJARO9le33BDXIyi0YuLW2nJFGLqkOvxFB0YPdBSaLZ0IwNzyPkO8-xkGgsLh8Al427a3hWAhXwwHA8EHT5PmgAB1bAQBAANJ24adKWpft72RaBUTgRBUCAj89HAM8xCTaBjggABRQx0DuHJv25P9dCkWRZVIAAiBjoFImpmjlFBgA0NpsjadByDacgIDAEAIAAQmYpjoGYgAZSBsmGPw6DtZiiFA8CoJguDmAQmoZ2QvtUKQLdoAYmBTwgdEiCAA)
|
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| 560 |
|
|---|
| 561 | ```ts
|
|---|
| 562 | class IdleService {
|
|---|
| 563 | doNothing (): void {}
|
|---|
| 564 | }
|
|---|
| 565 |
|
|---|
| 566 | class News {
|
|---|
| 567 | title: string;
|
|---|
| 568 | content: string;
|
|---|
| 569 |
|
|---|
| 570 | constructor(title: string, content: string) {
|
|---|
| 571 | this.title = title;
|
|---|
| 572 | this.content = content;
|
|---|
| 573 | }
|
|---|
| 574 | }
|
|---|
| 575 |
|
|---|
| 576 | const instanceCounter: Map<Function, number> = new Map();
|
|---|
| 577 |
|
|---|
| 578 | interface Constructor {
|
|---|
| 579 | new(...args: any[]): any;
|
|---|
| 580 | }
|
|---|
| 581 |
|
|---|
| 582 | // Keep track how many instances of `Constr` constructor have been created.
|
|---|
| 583 | function getInstance<
|
|---|
| 584 | Constr extends Constructor,
|
|---|
| 585 | Args extends ConstructorParameters<Constr>
|
|---|
| 586 | >(constructor: Constr, ...args: Args): InstanceType<Constr> {
|
|---|
| 587 | let count = instanceCounter.get(constructor) || 0;
|
|---|
| 588 |
|
|---|
| 589 | const instance = new constructor(...args);
|
|---|
| 590 |
|
|---|
| 591 | instanceCounter.set(constructor, count + 1);
|
|---|
| 592 |
|
|---|
| 593 | console.log(`Created ${count + 1} instances of ${Constr.name} class`);
|
|---|
| 594 |
|
|---|
| 595 | return instance;
|
|---|
| 596 | }
|
|---|
| 597 |
|
|---|
| 598 |
|
|---|
| 599 | const idleService = getInstance(IdleService);
|
|---|
| 600 | // Will log: `Created 1 instances of IdleService class`
|
|---|
| 601 | const newsEntry = getInstance(News, 'New ECMAScript proposals!', 'Last month...');
|
|---|
| 602 | // Will log: `Created 1 instances of News class`
|
|---|
| 603 | ```
|
|---|
| 604 | </details>
|
|---|
| 605 |
|
|---|
| 606 | - [`Omit<T, K>`](https://github.com/microsoft/TypeScript/blob/71af02f7459dc812e85ac31365bfe23daf14b4e4/src/lib/es5.d.ts#L1446) – Constructs a type by picking all properties from T and then removing K.
|
|---|
| 607 | <details>
|
|---|
| 608 | <summary>
|
|---|
| 609 | Example
|
|---|
| 610 | </summary>
|
|---|
| 611 |
|
|---|
| 612 | [Playground](https://typescript-play.js.org/?target=6#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-SgfXlHqVUE4xiAA)
|
|---|
| 613 |
|
|---|
| 614 | ```ts
|
|---|
| 615 | interface Animal {
|
|---|
| 616 | imageUrl: string;
|
|---|
| 617 | species: string;
|
|---|
| 618 | images: string[];
|
|---|
| 619 | paragraphs: string[];
|
|---|
| 620 | }
|
|---|
| 621 |
|
|---|
| 622 | // Creates new type with all properties of the `Animal` interface
|
|---|
| 623 | // except 'images' and 'paragraphs' properties. We can use this
|
|---|
| 624 | // type to render small hover tooltip for a wiki entry list.
|
|---|
| 625 | type AnimalShortInfo = Omit<Animal, 'images' | 'paragraphs'>;
|
|---|
| 626 |
|
|---|
| 627 | function renderAnimalHoverInfo (animals: AnimalShortInfo[]): HTMLElement {
|
|---|
| 628 | const container = document.createElement('div');
|
|---|
| 629 | // Internal implementation.
|
|---|
| 630 | return container;
|
|---|
| 631 | }
|
|---|
| 632 | ```
|
|---|
| 633 | </details>
|
|---|
| 634 |
|
|---|
| 635 | You can find some examples in the [TypeScript docs](https://www.typescriptlang.org/docs/handbook/advanced-types.html#predefined-conditional-types).
|
|---|
| 636 |
|
|---|
| 637 | ## Maintainers
|
|---|
| 638 |
|
|---|
| 639 | - [Sindre Sorhus](https://github.com/sindresorhus)
|
|---|
| 640 | - [Jarek Radosz](https://github.com/CvX)
|
|---|
| 641 | - [Dimitri Benin](https://github.com/BendingBender)
|
|---|
| 642 | - [Pelle Wessman](https://github.com/voxpelli)
|
|---|
| 643 |
|
|---|
| 644 | ## License
|
|---|
| 645 |
|
|---|
| 646 | (MIT OR CC0-1.0)
|
|---|
| 647 |
|
|---|
| 648 | ---
|
|---|
| 649 |
|
|---|
| 650 | <div align="center">
|
|---|
| 651 | <b>
|
|---|
| 652 | <a href="https://tidelift.com/subscription/pkg/npm-type-fest?utm_source=npm-type-fest&utm_medium=referral&utm_campaign=readme">Get professional support for this package with a Tidelift subscription</a>
|
|---|
| 653 | </b>
|
|---|
| 654 | <br>
|
|---|
| 655 | <sub>
|
|---|
| 656 | Tidelift helps make open source sustainable for maintainers while giving companies<br>assurances about security, maintenance, and licensing for their dependencies.
|
|---|
| 657 | </sub>
|
|---|
| 658 | </div>
|
|---|
