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This example demonstrates how to build a library with webpack that has dependencies to other libraries which should not be included in the compiled version.

We use the libraryTarget: "umd" option to build a UMD module that is consumable in CommonJs, AMD and with script tags. We don't specify the library option so the library is exported to the root namespace.

We use the externals option to define dependencies that should be resolved in the target environment.

In the simple case we just need to specify a string ("add"). Then it's resolved as "add" module in CommonJs and AMD, and as global add when used with script tag.

In the complex case we specify different values for each environment:

environment	config value	resolved as
CommonJs (strict)	`["./math", "subtract"]`	`require("./math").subtract`
CommonJs (node.js)	`"./subtract"`	`require("./subtract")`
AMD	`"subtract"`	`define(["subtract"], ...)`
script tag	`"subtract"`	`this.subtract`

example.js

var add = require("add");
var subtract = require("subtract");

exports.exampleValue = subtract(add(42, 2), 2);

webpack.config.js

module.exports = {
	// mode: "development || "production",
	output: {
		libraryTarget: "umd"
	},
	externals: [
		"add",
		{
			subtract: {
				root: "subtract",
				commonjs2: "./subtract",
				commonjs: ["./math", "subtract"],
				amd: "subtract"
			}
		}
	]
};

dist/output.js

(function webpackUniversalModuleDefinition(root, factory) {
	if(typeof exports === 'object' && typeof module === 'object')
		module.exports = factory(require("add"), require("./subtract"));
	else if(typeof define === 'function' && define.amd)
		define(["add", "subtract"], factory);
	else {
		var a = typeof exports === 'object' ? factory(require("add"), require("./math")["subtract"]) : factory(root["add"], root["subtract"]);
		for(var i in a) (typeof exports === 'object' ? exports : root)[i] = a[i];
	}
})(window, function(__WEBPACK_EXTERNAL_MODULE__1__, __WEBPACK_EXTERNAL_MODULE__2__) {
return /******/ (() => { // webpackBootstrap
/******/ 	var __webpack_modules__ = ([
/* 0 */
/*!********************!*\
  !*** ./example.js ***!
  \********************/
/*! exports [maybe provided (runtime-defined)] [maybe used (runtime-defined)] */
/*! runtime requirements: __webpack_require__, __webpack_exports__ */
/***/ ((__unused_webpack_module, exports, __webpack_require__) => {

var add = __webpack_require__(/*! add */ 1);
var subtract = __webpack_require__(/*! subtract */ 2);

exports.exampleValue = subtract(add(42, 2), 2);

/***/ }),
/* 1 */
/*!**********************!*\
  !*** external "add" ***!
  \**********************/
/*! exports [maybe provided (runtime-defined)] [no usage info] */
/*! runtime requirements: module */
/***/ ((module) => {

"use strict";
module.exports = __WEBPACK_EXTERNAL_MODULE__1__;

/***/ }),
/* 2 */
/*!***************************************************************************************************************!*\
  !*** external {"root":"subtract","commonjs2":"./subtract","commonjs":["./math","subtract"],"amd":"subtract"} ***!
  \***************************************************************************************************************/
/*! exports [maybe provided (runtime-defined)] [no usage info] */
/*! runtime requirements: module */
/***/ ((module) => {

"use strict";
module.exports = __WEBPACK_EXTERNAL_MODULE__2__;

/***/ })
/******/ 	]);

/* webpack runtime code */

/************************************************************************/
/******/ 	// The module cache
/******/ 	var __webpack_module_cache__ = {};
/******/ 	
/******/ 	// The require function
/******/ 	function __webpack_require__(moduleId) {
/******/ 		// Check if module is in cache
/******/ 		if(__webpack_module_cache__[moduleId]) {
/******/ 			return __webpack_module_cache__[moduleId].exports;
/******/ 		}
/******/ 		// Create a new module (and put it into the cache)
/******/ 		var module = __webpack_module_cache__[moduleId] = {
/******/ 			i: moduleId,
/******/ 			l: false,
/******/ 			exports: {}
/******/ 		};
/******/ 	
/******/ 		// Execute the module function
/******/ 		__webpack_modules__[moduleId](module, module.exports, __webpack_require__);
/******/ 	
/******/ 		// Flag the module as loaded
/******/ 		module.l = true;
/******/ 	
/******/ 		// Return the exports of the module
/******/ 		return module.exports;
/******/ 	}
/******/ 	
/************************************************************************/

/******/ 	// module exports must be returned from runtime so entry inlining is disabled
/******/ 	// startup
/******/ 	// Load entry module and return exports
/******/ 	return __webpack_require__(0);
/******/ })()
;
});

Info

Unoptimized

Hash: 0a1b2c3d4e5f6a7b8c9d
Version: webpack 5.0.0-beta.6
    Asset      Size
output.js  3.18 KiB  [emitted]  [name: main]
Entrypoint main = output.js
chunk output.js (main) 194 bytes [entry] [rendered]
    > ./example.js main
 ./example.js 110 bytes [built]
     entry ./example.js main
     used a library export
 external "add" 42 bytes [built]
     [used exports unknown]
     cjs require add ./example.js 1:10-24
 external {"root":"subtract","commonjs2":"./subtract","commonjs":["./math","subtract"],"amd":"subtract"} 42 bytes [built]
     [used exports unknown]
     cjs require subtract ./example.js 2:15-34

Production mode

Hash: 0a1b2c3d4e5f6a7b8c9d
Version: webpack 5.0.0-beta.6
    Asset       Size
output.js  668 bytes  [emitted]  [name: main]
Entrypoint main = output.js
chunk output.js (main) 194 bytes [entry] [rendered]
    > ./example.js main
 ./example.js 110 bytes [built]
     entry ./example.js main
     used a library export
 external "add" 42 bytes [built]
     cjs require add ./example.js 1:10-24
 external {"root":"subtract","commonjs2":"./subtract","commonjs":["./math","subtract"],"amd":"subtract"} 42 bytes [built]
     cjs require subtract ./example.js 2:15-34

6.1 KiB Raw Blame History