@jridgewell/gen-mapping

What is @jridgewell/gen-mapping?

The @jridgewell/gen-mapping package is a library for generating source maps, which are used to map the transformed source to the original source, enabling developers to debug their code more easily after it has been compiled or minified. It provides a simple API for adding mappings and generating the source map.

What are @jridgewell/gen-mapping's main functionalities?

Creating a new source map generator

This feature allows you to create a new source map generator instance, specifying the output file name for the source map.

{"const { GenMapping } = require('@jridgewell/gen-mapping');

const map = new GenMapping({
  file: 'minified.js'
});
}

Adding mappings to the source map

This feature allows you to add individual mappings to the source map, linking a location in the generated file to a location in the original source file.

{"const { addMapping } = require('@jridgewell/gen-mapping');

addMapping(map, {
  generated: { line: 1, column: 5 },
  source: 'original.js',
  original: { line: 1, column: 30 }
});
}

Generating the source map

This feature generates the final source map from the added mappings, which can then be used by browsers or other tools to map the transformed source back to the original source.

{"const { toMapping } = require('@jridgewell/gen-mapping');

const sourceMap = toMapping(map);
}

Other packages similar to @jridgewell/gen-mapping

source-map

The 'source-map' package provides similar functionality for generating source maps. It offers a more comprehensive API for manipulating source maps, including parsing and merging existing source maps, which @jridgewell/gen-mapping does not provide.

source-map-js

The 'source-map-js' package is a fork of the 'source-map' library that focuses on performance improvements and bug fixes. It is similar to @jridgewell/gen-mapping in that it generates source maps, but it also includes features for parsing and manipulating source maps.

magic-string

The 'magic-string' package is designed for manipulating strings and generating source maps in the process. It is different from @jridgewell/gen-mapping in that it provides a higher-level API for string manipulation, which includes source map generation as a byproduct of those manipulations.

README

@jridgewell/gen-mapping

Generate source maps

gen-mapping allows you to generate a source map during transpilation or minification. With a source map, you're able to trace the original location in the source file, either in Chrome's DevTools or using a library like @jridgewell/trace-mapping.

You may already be familiar with the source-map package's SourceMapGenerator. This provides the same addMapping and setSourceContent API.

Installation

npm install @jridgewell/gen-mapping

Usage

import { GenMapping, addMapping, setSourceContent, encodedMap } from '@jridgewell/gen-mapping';

const map = new GenMapping({
  file: 'output.js',
  sourceRoot: 'https://example.com/',
});

setSourceContent(map, 'input.js', `function foo() {}`);

addMapping(map, {
  // Lines start at line 1, columns at column 0.
  generated: { line: 1, column: 0 },
  source: 'input.js',
  original: { line: 1, column: 0 },
});

addMapping(map, {
  generated: { line: 1, column: 9 },
  source: 'input.js',
  original: { line: 1, column: 9 },
  name: 'foo',
});

assert.deepEqual(encodedMap(map), {
  version: 3,
  file: 'output.js',
  names: ['foo'],
  sourceRoot: 'https://example.com/',
  sources: ['input.js'],
  sourcesContent: ['function foo() {}'],
  mappings: 'AAAA,SAASA',
});