Replace loader for Webpack

Perform replacements (plain and regular expression) in the contents loaded by the loader.

Install:

$ yarn add --dev string-replace-loader

With release of 2.0.0 the loader is expected to be used in Node v4+ environment. Support for Node v3 and lower was dropped, but you can install and use the loader version of 1.3.0 in older environments.

With release of 3.0.0 the loader is expected to be used with Webpack v5+. Support for Webpack v4 and lower was dropped, but you can install and use the loader version of 2.3.0 in older environments.

Usage:

Loader allows to perform replacements in a way String.prototype.replace() does (loader uses it internally). It means that if you want to replace all occurrences, you should use RegExp-like string in options.search with g flag in options.flags, etc.

Plain replacement:

Plain string replacement, no need to escape RegEx special characters.

In your webpack.config.js:

module.exports = {
  // ...
  module: {
    rules: [
      {
        test: /fileInWhichJQueryIsUndefined\.js$/,
        loader: 'string-replace-loader',
        options: {
          search: '$',
          replace: 'window.jQuery',
        }
      }
    ]
  }
}

RegEx replacement:

To achieve regular expression replacement you should either specify the search option as RegExp instance, either specify it as string and add the flags option (as an empty string if you do not want any flags). In the latter case, search and flags are being passed to the RegExp constructor and this means that you should escape RegEx special characters in search if you want it to be replaced as a string.

In your webpack.config.js:

module.exports = {
  // ...
  module: {
    rules: [
      {
        test: /fileInWhichJQueryIsUndefined\.js$/,
        loader: 'string-replace-loader',
        options: {
          search: /\\$/i,
          replace: 'window.jQuery'
        }
      }
    ]
  }
}

or

module.exports = {
  // ...
  module: {
    rules: [
      {
        test: /fileInWhichJQueryIsUndefined\.js$/,
        loader: 'string-replace-loader',
        options: {
          search: '\\$',
          replace: 'window.jQuery',
          flags: 'i'
        }
      }
    ]
  }
}

Multiple replacement:

Also, you can pass an array of search-replace pairs this way:

In your webpack.config.js:

module.exports = {
  // ...
  module: {
    rules: [
      {
        test: /\.js$/,
        loader: 'string-replace-loader',
        options: {
          multiple: [
             { search: 'jQuery', replace: 'window.$' },
             { search: '_', replace: 'window.lodash' }
          ]
        }
      }
    ]
  }
}

Callback replacement

You can specify a callback function to have dynamic replacement values. The context of this function will be the context of the loader.

In your webpack.config.js:

module.exports = {
  // ...
  module: {
    rules: [
      {
        test: /\.js$/,
        loader: 'string-replace-loader',
        options: {
          search: '^Hello, (.*)!$',
          replace(match, p1, offset, string) {
            console.log(`Replace "${match}" in file "${this.resource}".`)
            return `Bonjour, ${p1.toUpperCase()}!`
          },
          flags: 'g'
        }
      }
    ]
  }
}

Strict mode replacement:

You can enable strict mode to ensure that the replacement was performed. Loader will throw exception if nothing was replaced or if search or replace options were not specified.

In your webpack.config.js:

module.exports = {
  // ...
  module: {
    rules: [
      {
        test: /fileInWhichJQueryIsUndefined\.js$/,
        loader: 'string-replace-loader',
        options: {
          search: 'jQuery',
          replace: 'window.$',
          strict: true
        }
      }
    ]
  }
}

Contributing:

Feel free to open issues to propose stuff and participate. Pull requests are also welcome.

Licence:

MIT