[d565449] | 1 | import debounce from './debounce.js';
|
---|
| 2 | import isObject from './isObject.js';
|
---|
| 3 |
|
---|
| 4 | /** Error message constants. */
|
---|
| 5 | var FUNC_ERROR_TEXT = 'Expected a function';
|
---|
| 6 |
|
---|
| 7 | /**
|
---|
| 8 | * Creates a throttled function that only invokes `func` at most once per
|
---|
| 9 | * every `wait` milliseconds. The throttled function comes with a `cancel`
|
---|
| 10 | * method to cancel delayed `func` invocations and a `flush` method to
|
---|
| 11 | * immediately invoke them. Provide `options` to indicate whether `func`
|
---|
| 12 | * should be invoked on the leading and/or trailing edge of the `wait`
|
---|
| 13 | * timeout. The `func` is invoked with the last arguments provided to the
|
---|
| 14 | * throttled function. Subsequent calls to the throttled function return the
|
---|
| 15 | * result of the last `func` invocation.
|
---|
| 16 | *
|
---|
| 17 | * **Note:** If `leading` and `trailing` options are `true`, `func` is
|
---|
| 18 | * invoked on the trailing edge of the timeout only if the throttled function
|
---|
| 19 | * is invoked more than once during the `wait` timeout.
|
---|
| 20 | *
|
---|
| 21 | * If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
|
---|
| 22 | * until to the next tick, similar to `setTimeout` with a timeout of `0`.
|
---|
| 23 | *
|
---|
| 24 | * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
|
---|
| 25 | * for details over the differences between `_.throttle` and `_.debounce`.
|
---|
| 26 | *
|
---|
| 27 | * @static
|
---|
| 28 | * @memberOf _
|
---|
| 29 | * @since 0.1.0
|
---|
| 30 | * @category Function
|
---|
| 31 | * @param {Function} func The function to throttle.
|
---|
| 32 | * @param {number} [wait=0] The number of milliseconds to throttle invocations to.
|
---|
| 33 | * @param {Object} [options={}] The options object.
|
---|
| 34 | * @param {boolean} [options.leading=true]
|
---|
| 35 | * Specify invoking on the leading edge of the timeout.
|
---|
| 36 | * @param {boolean} [options.trailing=true]
|
---|
| 37 | * Specify invoking on the trailing edge of the timeout.
|
---|
| 38 | * @returns {Function} Returns the new throttled function.
|
---|
| 39 | * @example
|
---|
| 40 | *
|
---|
| 41 | * // Avoid excessively updating the position while scrolling.
|
---|
| 42 | * jQuery(window).on('scroll', _.throttle(updatePosition, 100));
|
---|
| 43 | *
|
---|
| 44 | * // Invoke `renewToken` when the click event is fired, but not more than once every 5 minutes.
|
---|
| 45 | * var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
|
---|
| 46 | * jQuery(element).on('click', throttled);
|
---|
| 47 | *
|
---|
| 48 | * // Cancel the trailing throttled invocation.
|
---|
| 49 | * jQuery(window).on('popstate', throttled.cancel);
|
---|
| 50 | */
|
---|
| 51 | function throttle(func, wait, options) {
|
---|
| 52 | var leading = true,
|
---|
| 53 | trailing = true;
|
---|
| 54 |
|
---|
| 55 | if (typeof func != 'function') {
|
---|
| 56 | throw new TypeError(FUNC_ERROR_TEXT);
|
---|
| 57 | }
|
---|
| 58 | if (isObject(options)) {
|
---|
| 59 | leading = 'leading' in options ? !!options.leading : leading;
|
---|
| 60 | trailing = 'trailing' in options ? !!options.trailing : trailing;
|
---|
| 61 | }
|
---|
| 62 | return debounce(func, wait, {
|
---|
| 63 | 'leading': leading,
|
---|
| 64 | 'maxWait': wait,
|
---|
| 65 | 'trailing': trailing
|
---|
| 66 | });
|
---|
| 67 | }
|
---|
| 68 |
|
---|
| 69 | export default throttle;
|
---|