expose-loader

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

For further hints on compatibility issues, check out Shimming of the official docs.

Getting Started

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

1npm install expose-loader --save-dev

or

1yarn add -D expose-loader

or

1pnpm 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 is space in a query string, because you can't use spaces in URLs

1import $ from "expose-loader?exposes=$,jQuery!jquery";
2//
3// Adds the `jquery` to the global object under the names `$` and `jQuery`

1import { concat } from "expose-loader?exposes=_.concat!lodash/concat";
2//
3// Adds the `lodash/concat` to the global object under the name `_.concat`

1import {
2  map,
3  reduce,
4} from "expose-loader?exposes=_.map|map,_.reduce|reduce!underscore";
5//
6// Adds the `map` and `reduce` method from `underscore` to the global object under the name `_.map` and `_.reduce`

Using Configuration

src/index.js

1import $ from "jquery";

webpack.config.js

1module.exports = {
2  module: {
3    rules: [
4      {
5        test: require.resolve("jquery"),
6        loader: "expose-loader",
7        options: {
8          exposes: ["$", "jQuery"],
9        },
10      },
11      {
12        test: require.resolve("underscore"),
13        loader: "expose-loader",
14        options: {
15          exposes: [
16            "_.map|map",
17            {
18              globalName: "_.reduce",
19              moduleLocalName: "reduce",
20            },
21            {
22              globalName: ["_", "filter"],
23              moduleLocalName: "filter",
24            },
25          ],
26        },
27      },
28    ],
29  },
30};

The require.resolve call is a Node.js function (unrelated to require.resolve in webpack processing). require.resolve gives you the absolute path to 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.

And run webpack via your preferred method.

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:

1type exposes =
2  | string
3  | {
4      globalName: string | Array<string>;
5      moduleLocalName?: string;
6      override?: boolean;
7    }
8  | Array<
9      | string
10      | {
11          globalName: string | Array<string>;
12          moduleLocalName?: string;
13          override?: boolean;
14        }
15    >;

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 in 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

1import $ from "jquery";
2import _ from "underscore";

webpack.config.js

1module.exports = {
2  module: {
3    rules: [
4      {
5        test: require.resolve("jquery"),
6        loader: "expose-loader",
7        options: {
8          // For `underscore` library, it can be `_.map map` or `_.map|map`
9          exposes: "$",
10          // To access please use `window.$` or `globalThis.$`
11        },
12      },
13      {
14        // test: require.resolve("jquery"),
15        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
16        loader: "expose-loader",
17        type: "javascript/auto",
18        options: {
19          // For `underscore` library, it can be `_.map map` or `_.map|map`
20          exposes: "_",
21          // To access please use `window._` or `globalThis._`
22        },
23      },
24    ],
25  },
26};

object

Allows to use an object to describe an expose.

globalName

Type:

1type globalName = string | Array<string>;

Default: undefined

The name in the global object. (required).

src/index.js

1import _ from "underscore";

webpack.config.js

1module.exports = {
2  module: {
3    rules: [
4      {
5        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
6        loader: "expose-loader",
7        type: "javascript/auto",
8        options: {
9          exposes: {
10            // Can be `['_', 'filter']`
11            globalName: "_.filter",
12            moduleLocalName: "filter",
13          },
14        },
15      },
16    ],
17  },
18};

moduleLocalName

Type:

1type 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

1import _ from "underscore";

webpack.config.js

1module.exports = {
2  module: {
3    rules: [
4      {
5        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
6        loader: "expose-loader",
7        type: "javascript/auto",
8        options: {
9          exposes: {
10            globalName: "_.filter",
11            moduleLocalName: "filter",
12          },
13        },
14      },
15    ],
16  },
17};

override

Type:

1type 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

1import $ from "jquery";

webpack.config.js

1module.exports = {
2  module: {
3    rules: [
4      {
5        test: require.resolve("jquery"),
6        loader: "expose-loader",
7        options: {
8          exposes: {
9            globalName: "$",
10            override: true,
11          },
12        },
13      },
14    ],
15  },
16};

array

src/index.js

1import _ from "underscore";

webpack.config.js

1module.exports = {
2  module: {
3    rules: [
4      {
5        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
6        loader: "expose-loader",
7        type: "javascript/auto",
8        options: {
9          exposes: [
10            "_.map map",
11            {
12              globalName: "_.filter",
13              moduleLocalName: "filter",
14            },
15            {
16              globalName: ["_", "find"],
17              moduleLocalName: "myNameForFind",
18            },
19          ],
20        },
21      },
22    ],
23  },
24};

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

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

globalObject

1type globalObject = string;

Default: undefined

Object used for global context

1import _ from "underscore";

webpack.config.js

1module.exports = {
2  module: {
3    rules: [
4      {
5        test: /node_modules[/\\]underscore[/\\]modules[/\\]index-all\.js$/,
6        loader: "expose-loader",
7        type: "javascript/auto",
8        options: {
9          exposes: [
10            {
11              globalName: "_",
12            },
13          ],
14          globalObject: "this",
15        },
16      },
17    ],
18  },
19};

Examples

Expose a local module

index.js

1import { method1 } from "./my-module.js";

my-module.js

1function method1() {
2  console.log("method1");
3}
4
5function method2() {
6  console.log("method1");
7}
8
9export { method1, method2 };

webpack.config.js

1module.exports = {
2  module: {
3    rules: [
4      {
5        test: /my-module\.js$/,
6        loader: "expose-loader",
7        options: {
8          exposes: "mod",
9          // // To access please use `window.mod` or `globalThis.mod`
10        },
11      },
12    ],
13  },
14};

Contributing

Please take a moment to read our contributing guidelines if you haven't yet done so.

CONTRIBUTING

License

MIT