imports-loader

What is imports-loader?

The imports-loader npm package allows you to use custom imports in your modules. It is particularly useful for injecting variables or dependencies into modules that do not explicitly export them, or for polyfilling global variables.

What are imports-loader's main functionalities?

Injecting Variables

This feature allows you to inject variables into your modules. In this example, the jQuery library is injected into every JavaScript file, making the $ variable available globally.

module.exports = {
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        use: [
          {
            loader: 'imports-loader',
            options: {
              additionalCode: 'var $ = require("jquery");'
            }
          }
        ]
      }
    ]
  }
};

Polyfilling Global Variables

This feature allows you to polyfill global variables that may not be available in certain environments. In this example, the process variable is polyfilled using the 'process/browser' module.

module.exports = {
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        use: [
          {
            loader: 'imports-loader',
            options: {
              additionalCode: 'var process = require("process/browser");'
            }
          }
        ]
      }
    ]
  }
};

Injecting Dependencies

This feature allows you to inject dependencies into your modules. In this example, the lodash library is injected into every JavaScript file, making the _ variable available globally.

module.exports = {
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        use: [
          {
            loader: 'imports-loader',
            options: {
              imports: {
                moduleName: 'lodash',
                name: '_'
              }
            }
          }
        ]
      }
    ]
  }
};

Other packages similar to imports-loader

expose-loader

The expose-loader package allows you to expose a module globally, making it available as a global variable. This is similar to the imports-loader's ability to inject variables, but expose-loader is more focused on making specific modules globally accessible.

script-loader

The script-loader package allows you to add scripts to your bundle as a string. This can be useful for injecting scripts that are not available as modules. While imports-loader focuses on injecting variables and dependencies, script-loader is more about adding raw script content.

README

imports-loader

The imports loader allows you to use modules that depend on specific global variables.

This is useful for third-party modules that rely on global variables like $ or this being the window object. The imports loader can add the necessary require('whatever') calls, so those modules work with webpack.

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

Warning

By default loader generate ES module named syntax.

Warning

Be careful, existing imports (import/require) in the original code and importing new values can cause failure.

Getting Started

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

npm install imports-loader --save-dev

or

yarn add -D imports-loader

or

pnpm add -D imports-loader

Given you have this file:

example.js

$("img").doSomeAwesomeJqueryPluginStuff();

Then you can inject the jquery value into the module by configuring the imports-loader using two approaches.

Inline

The | or %20 (space) allow to separate the syntax, moduleName, name and alias of import. 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

// Alternative syntax:
//
// import myLib from 'imports-loader?imports=default%20jquery%20$!./example.js';
//
// `%20` is space in a query string, equivalently `default jquery $`
import myLib from "imports-loader?imports=default|jquery|$!./example.js";
// Adds the following code to the beginning of example.js:
//
// import $ from "jquery";
//
// ...
// Code
// ...

import myLib from "imports-loader?imports=default|jquery|$,angular!./example.js";
// `|` is separator in a query string, equivalently `default|jquery|$` and `angular`
// Adds the following code to the beginning of example.js:
//
// import $ from "jquery";
// import angular from "angular";
//
// ...
// Code
// ...

import myLib from "imports-loader?imports=named|library|myMethod,angular!./example.js";
// `|` is separator in a query string, equivalently `named|library|myMethod` and `angular`
// Adds the following code to the beginning of example.js:
//
// import { myMethod } from "library";
// import angular from "angular";
//
// ...
// Code
// ...

const myLib = require(`imports-loader?type=commonjs&imports=single|jquery|$,angular!./example.js`);
// `|` is separator in a query string, equivalently `single|jquery|$` and `angular`
// Adds the following code to the beginning of example.js:
//
// var $ = require("jquery");
// var angular = require("angular");
//
// ...
// Code
// ...

const myLib = require(`imports-loader?type=commonjs&imports=single|myLib|myMethod&wrapper=window&!./example.js`);
// `|` is separator in a query string, equivalently `single|myLib|myMethod` and `angular`
// Adds the following code to the example.js:
//
// const myMethod = require('myLib');
//
// (function () {
// ...
// Code
// ...
// }.call(window));

import myLib from "imports-loader?additionalCode=var%20myVariable%20=%20false;!./example.js";
// Adds the following code to the beginning of example.js:
//
// var myVariable = false;
//
// ...
// Code
// ...

Using Configuration

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        // You can use `regexp`
        // test: /example\.js/$
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: [
                "default jquery $",
                "default lib_2 lib_2_default",
                "named lib_3 lib2_method_1",
                "named lib_3 lib2_method_2 lib_2_method_2_short",
                "namespace lib_4 my_namespace",
                "side-effects lib_5",
                {
                  syntax: "default",
                  moduleName: "angular",
                  name: "angular",
                },
              ],
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import $ from "jquery";
import lib_2_default from "lib_2";
import { lib2_method_1, lib2_method_2 as lib_2_method_2_short } from "lib_3";
import * as my_namespace from "lib_4";
import "lib_5";
import angular from "angular";

And run webpack via your preferred method.

Options

• type
• imports
• wrapper
• additionalCode

type

Type:

type type = string;

Default: module

Format of generated exports.

Possible values - commonjs (CommonJS module syntax) and module (ES module syntax).

commonjs

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        loader: "imports-loader",
        options: {
          syntax: "default",
          type: "commonjs",
          imports: "Foo",
        },
      },
    ],
  },
};

Generate output:

var Foo = require("Foo");

// ...
// Code
// ...

module

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        loader: "imports-loader",
        options: {
          type: "module",
          imports: "Foo",
        },
      },
    ],
  },
};

Generate output:

import Foo from "Foo";

// ...
// Code
// ...

imports

Type:

type imports =
  | string
  | {
      syntax:
        | "default"
        | "named"
        | "namespace"
        | "side-effects"
        | "single"
        | "multiple"
        | "pure";
      moduleName: string;
      name: string;
      alias: string;
    }
  | Array<
      | string
      | {
          syntax:
            | "default"
            | "named"
            | "namespace"
            | "side-effects"
            | "single"
            | "multiple"
            | "pure";
          moduleName: string;
          name: string;
          alias: string;
        }
    >;

Default: undefined

List of imports.

string

Allows to use a string to describe an export.

Syntax

The | or %20 (space) allow to separate the syntax, moduleName, name and alias of import.

String syntax - [[syntax] [moduleName] [name] [alias]] or [[syntax]|[moduleName]|[name]|[alias]], where:

• [syntax] (may be omitted):

  • if type is module- can be default, named, namespace or side-effects, the default value is default.
  • if type is commonjs- can be single, multiple or pure, the default value is single.

• [moduleName] - name of an imported module (required)

• [name] - name of an imported value (required)

• [alias] - alias of an imported value (may be omitted)

Examples:

If type module:

• [Foo] - generates import Foo from "Foo";.
• [default Foo] - generates import Foo from "Foo";.
• [default ./my-lib Foo] - generates import Foo from "./my-lib";.
• [named Foo FooA] - generates import { FooA } from "Foo";.
• [named Foo FooA Bar] - generates import { FooA as Bar } from "Foo";.
• [namespace Foo FooA] - generates import * as FooA from "Foo";.
• [side-effects Foo] - generates import "Foo";.

If type commonjs:

• [Foo] - generates const Foo = require("Foo");.
• [single Foo] - generates const Foo = require("Foo");.
• [single ./my-lib Foo] - generates const Foo = require("./my-lib");.
• [multiple Foo FooA Bar] - generates const { FooA: Bar } = require("Foo");.
• [pure Foo] - generates require("Foo");.

Warning

You need to set type: "commonjs" to use single, multiple and pure syntaxes.

Warning

Aliases can't be used together with default, namespace, side-effects, single and pure syntaxes.

Examples

ES Module Default Import

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("./path/to/example.js"),
        loader: "imports-loader",
        options: {
          imports: "default lib myName",
        },
      },
    ],
  },
};

Generate output:

import myName from "lib";

// ...
// Code
// ...

CommonJS Single Import

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("./path/to/example.js"),
        loader: "imports-loader",
        options: {
          type: "commonjs",
          imports: "single lib myName",
        },
      },
    ],
  },
};

Generate output:

var myName = require("lib");

// ...
// Code
// ...

object

Allows to use an object to describe an import.

Properties:

• syntax:

  • if type is module- can be default, named, namespace or side-effects
  • if type is commonjs- can be single, multiple or pure

• moduleName - name of an imported module (required)

• name - name of an imported value (required)

• alias - alias of an imported value (may be omitted)

Warning

Alias can't be used together with default, namespace, side-effects, single and pure syntaxes.

Examples

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: {
                syntax: "named",
                moduleName: "lib_2",
                name: "lib2_method_2",
                alias: "lib_2_method_2_alias",
              },
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import { lib2_method_2 as lib_2_method_2_alias } from "lib_2";

// ...
// Code
// ...

array

Allow to specify multiple imports. Each item can be a string or an object.

Examples

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: [
                {
                  moduleName: "angular",
                },
                {
                  syntax: "default",
                  moduleName: "jquery",
                  name: "$",
                },
                "default lib_2 lib_2_default",
                "named lib_2 lib2_method_1",
                "named lib_2 lib2_method_2 lib_2_method_2_alias",
                "namespace lib_3 lib_3_all",
                "side-effects lib_4",
              ],
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import angular from "angular";
import $ from "jquery";
import lib_2_default from "lib_2";
import { lib2_method_1, lib2_method_2 as lib_2_method_2_alias } from "lib_2";
import * as lib_3_all from "lib_3";
import "lib_4";

// ...
// Code
// ...

wrapper

Type:

type wrapper =
  | boolean
  | string
  | {
      thisArg: string;
      args: Record<string, string> | Array<string>;
    };

Default: undefined

Closes the module code in a function with a given thisArg and args ((function () { ... }).call();).

Warning

Do not use this option if source code contains ES module import(s)

boolean

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: {
                moduleName: "jquery",
                name: "$",
              },
              wrapper: true,
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import $ from "jquery";

(function () {
  // ...
  // Code
  // ...
}.call());

string

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: {
                moduleName: "jquery",
                name: "$",
              },
              wrapper: "window",
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import $ from "jquery";

(function () {
  // ...
  // Code
  // ...
}.call(window));

object

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: {
                moduleName: "jquery",
                name: "$",
              },
              wrapper: {
                thisArg: "window",
                args: ["myVariable", "myOtherVariable"],
              },
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import $ from "jquery";

(function (myVariable, myOtherVariable) {
  // ...
  // Code
  // ...
}.call(window, myVariable, myOtherVariable));

object with different parameter names

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: {
                moduleName: "jquery",
                name: "$",
              },
              wrapper: {
                thisArg: "window",
                args: {
                  myVariable: "var1",
                  myOtherVariable: "var2",
                },
              },
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import $ from "jquery";

(function (var1, var2) {
  // ...
  // Code
  // ...
}.call(window, myVariable, myOtherVariable));

additionalCode

Type:

type additionalCode = string;

Default: undefined

Adds custom code as a preamble before the module's code.

Examples

Define custom variable

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: {
                moduleName: "jquery",
                name: "$",
              },
              additionalCode: "var myVariable = false;",
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import $ from "jquery";

var myVariable = false;

// ...
// Code
// ...

Disable AMD Import Syntax

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: require.resolve("example.js"),
        use: [
          {
            loader: "imports-loader",
            options: {
              imports: {
                moduleName: "jquery",
                name: "$",
              },
              additionalCode:
                "var define = false; /* Disable AMD for misbehaving libraries */",
            },
          },
        ],
      },
    ],
  },
};

Generate output:

import $ from "jquery";

var define = false; /* Disable AMD for misbehaving libraries */

// ...
// Code
// ...

Contributing

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

CONTRIBUTING

License

MIT

Changelog

4.0.1 (2022-08-12)

Bug Fixes

• source map for other loaders (#146) (5a1f866)