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    sourcemap-codec
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    1.4.6 • Public • Published

    sourcemap-codec

    Encode/decode the mappings property of a sourcemap.

    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. 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

    npm install sourcemap-codec

    Usage

    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

    Keywords

    Install

    npm i sourcemap-codec@1.4.6

    Version

    1.4.6

    License

    MIT

    Unpacked Size

    15.6 kB

    Total Files

    7

    Last publish

    Collaborators

    • rich_harris