expose-loader

Disclaimer: expose-loader is a third-party package maintained by community members, it potentially does not have the same support, security policy or license as webpack, and it is not maintained by webpack.

The expose-loader loader allows to expose a module (either in whole or in part) to global object (self, window and global).

For compatibility tips and examples, check out Shimming guide in the official documentation.

Getting Started

To begin, you'll need to install expose-loader:

npm install expose-loader --save-dev

yarn add -D expose-loader

pnpm add -D expose-loader

(If you're using webpack 4, install expose-loader@1 and follow the corresponding instructions instead.)

Then you can use the expose-loader using two approaches.

Inline

The | or %20 (space) allow to separate the globalName, moduleLocalName and override of expose.

The documentation and syntax examples can be read here.

[!WARNING]

%20 represents a space in a query string because spaces are not allowed in URLs.

import $ from "expose-loader?exposes=$,jQuery!jquery";
//
// Adds the `jquery` to the global object under the names `$` and `jQuery`

import { concat } from "expose-loader?exposes=_.concat!lodash/concat";
//
// Adds the `lodash/concat` to the global object under the name `_.concat`

import {
  map,
  reduce,
} from "expose-loader?exposes=_.map|map,_.reduce|reduce!underscore";
//
// Adds the `map` and `reduce` method from `underscore` to the global object under the name `_.map` and `_.reduce`

Using Configuration

src/index.js

import $ from "jquery";

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("jquery"),
        loader: "expose-loader",
        options: {
          exposes: ["$", "jQuery"],
        },
      },
      {
        test: require.resolve("underscore"),
        loader: "expose-loader",
        options: {
          exposes: [
            "_.map|map",
            {
              globalName: "_.reduce",
              moduleLocalName: "reduce",
            },
            {
              globalName: ["_", "filter"],
              moduleLocalName: "filter",
            },
          ],
        },
      },
    ],
  },
};

The require.resolve call is a Node.js function (unrelated to require.resolve in webpack processing).

require.resolve that returns the absolute path of the module ("/.../app/node_modules/jquery/dist/jquery.js").

So the expose only applies to the jquery module and it's only exposed when used in the bundle.

Finally, run webpack using the method you normally use (e.g., via CLI or an npm script).

Options

Name	Type	Default	Description
`exposes`	`{String\|Object\|Array<String\|Object>}`	`undefined`	List of exposes
`globalObject`	`String`	`undefined`	Object used for global context

`exposes`

Type:

type exposes =
  | string
  | {
      globalName: string | string[];
      moduleLocalName?: string;
      override?: boolean;
    }
  | (
      | string
      | {
          globalName: string | string[];
          moduleLocalName?: string;
          override?: boolean;
        }
    )[];

Default: undefined

List of exposes.

`string`

Allows to use a string to describe an expose.

`syntax`

The | or %20 (space) allow to separate the globalName, moduleLocalName and override of expose.

String syntax - [[globalName] [moduleLocalName] [override]] or [[globalName]|[moduleLocalName]|[override]], where:

globalName - The name on the global object, for example window.$ for a browser environment (required)
moduleLocalName - The name of method/variable etc of the module (the module must export it) (may be omitted)
override - Allows to override existing value in the global object (may be omitted)

If moduleLocalName is not specified, it exposes the entire module to the global object, otherwise it exposes only the value of moduleLocalName.

src/index.js

import $ from "jquery";
import _ from "underscore";

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("jquery"),
        loader: "expose-loader",
        options: {
          // For `underscore` library, it can be `_.map map` or `_.map|map`
          exposes: "$",
          // To access please use `window.$` or `globalThis.$`
        },
      },
      {
        // test: require.resolve("jquery"),
        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
        loader: "expose-loader",
        type: "javascript/auto",
        options: {
          // For `underscore` library, it can be `_.map map` or `_.map|map`
          exposes: "_",
          // To access please use `window._` or `globalThis._`
        },
      },
    ],
  },
};

`object`

Allows to use an object to describe an expose.

`globalName`

Type:

type globalName = string | string[];

Default: undefined

The name in the global object. (required).

src/index.js

import _ from "underscore";

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
        loader: "expose-loader",
        type: "javascript/auto",
        options: {
          exposes: {
            // Can be `['_', 'filter']`
            globalName: "_.filter",
            moduleLocalName: "filter",
          },
        },
      },
    ],
  },
};

`moduleLocalName`

Type:

type moduleLocalName = string;

Default: undefined

The name of method/variable etc of the module (the module must export it).

If moduleLocalName is specified, it exposes only the value of moduleLocalName.

src/index.js

import _ from "underscore";

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
        loader: "expose-loader",
        type: "javascript/auto",
        options: {
          exposes: {
            globalName: "_.filter",
            moduleLocalName: "filter",
          },
        },
      },
    ],
  },
};

`override`

Type:

type override = boolean;

Default: false

By default, loader does not override the existing value in the global object, because it is unsafe.

In development mode, we throw an error if the value already present in the global object.

But you can configure loader to override the existing value in the global object using this option.

To force override the value that is already present in the global object you can set the override option to the true value.

src/index.js

import $ from "jquery";

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("jquery"),
        loader: "expose-loader",
        options: {
          exposes: {
            globalName: "$",
            override: true,
          },
        },
      },
    ],
  },
};

`array`

src/index.js

import _ from "underscore";

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
        loader: "expose-loader",
        type: "javascript/auto",
        options: {
          exposes: [
            "_.map map",
            {
              globalName: "_.filter",
              moduleLocalName: "filter",
            },
            {
              globalName: ["_", "find"],
              moduleLocalName: "myNameForFind",
            },
          ],
        },
      },
    ],
  },
};

It will expose only map, filter and find (under myNameForFind name) methods to the global object.

In browsers, these methods will be available under windows._.map(..args), windows._.filter(...args) and windows._.myNameForFind(...args) methods.

`globalObject`

type globalObject = string;

Default: undefined

Object used for global context

import _ from "underscore";

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
        loader: "expose-loader",
        type: "javascript/auto",
        options: {
          exposes: [
            {
              globalName: "_",
            },
          ],
          globalObject: "this",
        },
      },
    ],
  },
};

Examples

Expose a local module

index.js

import { method1 } from "./my-module.js";

my-module.js

function method1() {
  console.log("method1");
}

function method2() {
  console.log("method1");
}

export { method1, method2 };

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /my-module\.js$/,
        loader: "expose-loader",
        options: {
          exposes: "mod",
          // // To access please use `window.mod` or `globalThis.mod`
        },
      },
    ],
  },
};

Contributing

We welcome all contributions!

If you're new here, please take a moment to review our contributing guidelines before submitting issues or pull requests.

CONTRIBUTING

License

MIT

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