NormalModuleReplacementPlugin

The NormalModuleReplacementPlugin allows you to replace resources that match resourceRegExp with newResource. If newResource is relative, it is resolved relative to the previous resource. If newResource is a function, it is expected to overwrite the request attribute of the supplied resource.

This can be useful for allowing different behaviour between builds.

new webpack.NormalModuleReplacementPlugin(resourceRegExp, newResource);

Note that the resourceRegExp is tested against the request you write in your code, not the resolved resource. For instance, './sum' will be used to test instead of './sum.js' when you have code import sum from './sum'.

Also please note that when using Windows, you have to accomodate for the different folder separator symbol. E.g. /src\/environments\/environment\.ts/ won't work on Windows, you have to use /src[\\/]environments[\\/]environment\.ts/, instead.

Basic Example

Replace a specific module when building for a development environment.

Say you have a configuration file some/path/config.development.module.js and a special version for production in some/path/config.production.module.js

Add the following plugin when building for production:

new webpack.NormalModuleReplacementPlugin(
  /some\/path\/config\.development\.js/,
  './config.production.js'
);

Advanced Example

Conditional build depending on an specified environment.

Say you want a configuration with specific values for different build targets.

module.exports = function (env) {
  var appTarget = env.APP_TARGET || 'VERSION_A';
  return {
    plugins: [
      new webpack.NormalModuleReplacementPlugin(
        /(.*)-APP_TARGET(\.*)/,
        function (resource) {
          resource.request = resource.request.replace(
            /-APP_TARGET/,
            `-${appTarget}`
          );
        }
      ),
    ],
  };
};

Create the two configuration files:

app/config-VERSION_A.js

export default {
  title: 'I am version A',
};

app/config-VERSION_B.js

export default {
  title: 'I am version B',
};

Then import that configuration using the keyword you're looking for in the regexp:

import config from 'app/config-APP_TARGET';
console.log(config.title);

And now you get the right configuration imported depending on which target you're building for:

npx webpack --env APP_TARGET=VERSION_A
=> 'I am version A'

npx webpack --env APP_TARGET=VERSION_B
=> 'I am version B'