source: trip-planner-front/node_modules/sourcemap-codec/README.md@ bdd6491

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1# sourcemap-codec
2
3Encode/decode the `mappings` property of a [sourcemap](https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit).
4
5
6## Why?
7
8Sourcemaps are difficult to generate and manipulate, because the `mappings` property – the part that actually links the generated code back to the original source – is encoded using an obscure method called [Variable-length quantity](https://en.wikipedia.org/wiki/Variable-length_quantity). On top of that, each segment in the mapping contains offsets rather than absolute indices, which means that you can't look at a segment in isolation – you have to understand the whole sourcemap.
9
10This package makes the process slightly easier.
11
12
13## Installation
14
15```bash
16npm install sourcemap-codec
17```
18
19
20## Usage
21
22```js
23import { encode, decode } from 'sourcemap-codec';
24
25var decoded = decode( ';EAEEA,EAAE,EAAC,CAAE;ECQY,UACC' );
26
27assert.deepEqual( decoded, [
28 // the first line (of the generated code) has no mappings,
29 // as shown by the starting semi-colon (which separates lines)
30 [],
31
32 // the second line contains four (comma-separated) segments
33 [
34 // segments are encoded as you'd expect:
35 // [ generatedCodeColumn, sourceIndex, sourceCodeLine, sourceCodeColumn, nameIndex ]
36
37 // i.e. the first segment begins at column 2, and maps back to the second column
38 // of the second line (both zero-based) of the 0th source, and uses the 0th
39 // name in the `map.names` array
40 [ 2, 0, 2, 2, 0 ],
41
42 // the remaining segments are 4-length rather than 5-length,
43 // because they don't map a name
44 [ 4, 0, 2, 4 ],
45 [ 6, 0, 2, 5 ],
46 [ 7, 0, 2, 7 ]
47 ],
48
49 // the final line contains two segments
50 [
51 [ 2, 1, 10, 19 ],
52 [ 12, 1, 11, 20 ]
53 ]
54]);
55
56var encoded = encode( decoded );
57assert.equal( encoded, ';EAEEA,EAAE,EAAC,CAAE;ECQY,UACC' );
58```
59
60
61# License
62
63MIT
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