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