karma-sourcemap-loader

What is karma-sourcemap-loader?

The karma-sourcemap-loader is an npm package that preprocesses source maps for your files, allowing you to debug your original source code in the browser when running tests with Karma. This is particularly useful for projects that use transpilers or minifiers, as it helps map the compiled code back to the original source code.

What are karma-sourcemap-loader's main functionalities?

Preprocessing Source Maps

This feature allows you to preprocess source maps for your JavaScript files. By adding 'sourcemap' to the preprocessors array, karma-sourcemap-loader will handle the source maps, enabling you to debug the original source code in the browser.

module.exports = function(config) {
  config.set({
    preprocessors: {
      'src/**/*.js': ['sourcemap']
    },
    files: [
      'src/**/*.js',
      'test/**/*.spec.js'
    ],
    // other configurations
  });
};

Other packages similar to karma-sourcemap-loader

karma-webpack

karma-webpack is a Karma plugin that allows you to use Webpack to preprocess your files before running tests. It can handle source maps similarly to karma-sourcemap-loader, but it also provides additional features like module bundling and asset management.

karma-browserify

karma-browserify is another Karma plugin that uses Browserify to preprocess your files. It supports source maps and allows you to use Node.js-style require statements in your tests. It is similar to karma-sourcemap-loader but offers more flexibility in terms of module bundling.

karma-rollup-preprocessor

karma-rollup-preprocessor is a Karma plugin that uses Rollup to preprocess your files. It supports source maps and is particularly useful for projects that use ES6 modules. It offers similar functionality to karma-sourcemap-loader but with the added benefits of Rollup's tree-shaking and code-splitting capabilities.

README

karma-sourcemap-loader

Preprocessor that locates and loads existing source maps.

Why

When you use karma not in isolation but as part of a build process (e.g. using grunt or gulp) it is often the case that the compilation/transpilation is done on a previous step of the process and not handled by karma preprocessors. In these cases source maps don't get loaded by karma and you lose the advantages of having them.

How it works

This plug-in supports both inline and external source maps.

Inline source maps are located by searching "sourceMappingURL=" inside the javascript file, both plain text and base64-encoded maps are supported.

External source maps are located by appending ".map" to the javascript file name. So if for example you have Hello.js, the preprocessor will try to load source map from Hello.js.map.

Installation

Just write karma-sourcemap-loader as a devDependency in your package.json.

{
  "devDependencies": {
    "karma-sourcemap-loader": "~0.2"
  }
}

Or just issue the following command:

npm install karma-sourcemap-loader --save-dev

Configuration

The code below shows a sample configuration of the preprocessor.

// karma.conf.js
module.exports = function(config) {
  config.set({
    preprocessors: {
      '**/*.js': ['sourcemap']
    }
  });
};

Credits

Thanks to @goldibex for adding inline source maps support.