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- # sourcemap-codec
- Encode/decode the `mappings` property of a [sourcemap](https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit).
- ## Why?
- Sourcemaps 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.
- This package makes the process slightly easier.
- ## Installation
- ```bash
- npm install sourcemap-codec
- ```
- ## Usage
- ```js
- import { encode, decode } from 'sourcemap-codec';
- var decoded = decode( ';EAEEA,EAAE,EAAC,CAAE;ECQY,UACC' );
- assert.deepEqual( decoded, [
- // the first line (of the generated code) has no mappings,
- // as shown by the starting semi-colon (which separates lines)
- [],
- // the second line contains four (comma-separated) segments
- [
- // segments are encoded as you'd expect:
- // [ generatedCodeColumn, sourceIndex, sourceCodeLine, sourceCodeColumn, nameIndex ]
- // i.e. the first segment begins at column 2, and maps back to the second column
- // of the second line (both zero-based) of the 0th source, and uses the 0th
- // name in the `map.names` array
- [ 2, 0, 2, 2, 0 ],
- // the remaining segments are 4-length rather than 5-length,
- // because they don't map a name
- [ 4, 0, 2, 4 ],
- [ 6, 0, 2, 5 ],
- [ 7, 0, 2, 7 ]
- ],
- // the final line contains two segments
- [
- [ 2, 1, 10, 19 ],
- [ 12, 1, 11, 20 ]
- ]
- ]);
- var encoded = encode( decoded );
- assert.equal( encoded, ';EAEEA,EAAE,EAAC,CAAE;ECQY,UACC' );
- ```
- # License
- MIT
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