Sign Up for Free

RunKit +

Try any Node.js package right in your browser

This is a playground to test code. It runs a full Node.js environment and already has all of npm’s 400,000 packages pre-installed, including karma-sourcemap-loader with all npm packages installed. Try it out:

var karmaSourcemapLoader = require("karma-sourcemap-loader")

This service is provided by RunKit and is not affiliated with npm, Inc or the package authors.

karma-sourcemap-loader v0.3.7

Karma plugin that locates and loads existing javascript source map files.


Preprocessor that locates and loads existing source maps.


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


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

  "devDependencies": {
    "karma-sourcemap-loader": "~0.3"

Or issue the following command:

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


The code below shows a sample configuration of the preprocessor.

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


RunKit is a free, in-browser JavaScript dev environment for prototyping Node.js code, with every npm package installed. Sign up to share your code.
Sign Up for Free