source-map-loader extracts existing source maps from all JavaScript entries in your project. This includes both inline source maps as well as those that are externally loaded. All source map data is processed as per a chosen source map style, which you specify with the devtool option in webpack.config.js. The following code shows that configuration:

module.exports = {
     module: {
     rules: [
     {
       test: /.script.js$/,
       use: [
   {
     loader: 'script-loader',
     options: {
           sourceMap: true,
              },
   },
        ]
    }
         ]
    }
 }

This loader can be extremely useful when using third-party libraries that have source maps. If not extracted and processed into the source map of the bundle, browsers may interpret source map data incorrectly. This loader allows the maintenance of source map data continuity across libraries and frameworks to ensure easy debugging.

The loader will extract from any JavaScript file, including those in the node_modules directory. Care should be taken when setting include and exclude rule conditions to optimize bundling performance.