移除未使用的代码

example.js

  1. const inc = require("./increment").increment;
  2. var a = 1;
  3. inc(a); // 2

increment.js

  1. const add = require("./math").add;
  2. exports.increment = function increment(val) {
  3. return add(val, 1);
  4. };
  5. exports.incrementBy2 = function incrementBy2(val) {
  6. return add(val, 2);
  7. };
  8. exports.decrement = function decrement(val) {
  9. return add(val, 1);
  10. };

math.js

  1. exports.add = function add() {
  2. var sum = 0,
  3.      i = 0,
  4.      args = arguments,
  5.      l = args.length;
  6. while (i < l) {
  7.      sum += args[i++];
  8. }
  9. return sum;
  10. };
  11. exports.multiply = function multiply() {
  12. var product = 0,
  13.      i = 0,
  14.      args = arguments,
  15.      l = args.length;
  16. while (i < l) {
  17.      sum *= args[i++];
  18. }
  19. return sum;
  20. };

webpack.config.js

  1. module.exports = [
  2.     {
  3.         entry: "./example.js",
  4.         output: {
  5.             pathinfo: true,
  6.             filename: "output.js"
  7.         },
  8.         optimization: {
  9.             moduleIds: "size",
  10.             usedExports: true,
  11.             mangleExports: true
  12.         }
  13.     },
  14.     {
  15.         entry: "./example.js",
  16.         output: {
  17.             pathinfo: true,
  18.             filename: "without.js"
  19.         },
  20.         optimization: {
  21.             moduleIds: "size",
  22.             usedExports: false,
  23.             mangleExports: false
  24.         }
  25.     }
  26. ];

usedExports可以告诉webpack生成模块导出和使用的信息，这个信息会被其他优化配置项或其他插件使用。、mangleExports 告诉webpack是否将导出的模块名称简写。打包后的文件。
可以看到每个模块的上边都有注释信息，未使用的被标记 [unused]
导出的模块名也被简写了（Mj, nP, nP）
/! default exports /
/! export decrement [provided] [unused] [renamed to Mj] /
/! export increment [provided] [used in main] [renamed to nP] /
/! export incrementBy2 [provided] [unused] [renamed to pN] /

  1. /******/ (() => { // webpackBootstrap
  2. /******/     var __webpack_modules__ = ([
  3. /* 0 */,
  4. /* 1 */
  5. /*!**********************!*\
  6.   !*** ./increment.js ***!
  7.   \**********************/
  8. /*! default exports */
  9. /*! export decrement [provided] [unused] [renamed to Mj] */
  10. /*! export increment [provided] [used in main] [renamed to nP] */
  11. /*! export incrementBy2 [provided] [unused] [renamed to pN] */
  12. /*! runtime requirements: __webpack_require__, __webpack_exports__ */
  13. /***/ ((__unused_webpack_module, exports, __webpack_require__) => {
  15. var __webpack_unused_export__;
  16. const add = __webpack_require__(/*! ./math */ 2)/* .add */ .I;
  17. exports.nP = function increment(val) {
  18.     return add(val, 1);
  19. };
  20. __webpack_unused_export__ = function incrementBy2(val) {
  21.     return add(val, 2);
  22. };
  23. __webpack_unused_export__ = function decrement(val) {
  24.     return add(val, 1);
  25. };
  28. /***/ }),
  29. /* 2 */
  30. /*!*****************!*\
  31.   !*** ./math.js ***!
  32.   \*****************/
  33. /*! default exports */
  34. /*! export add [provided] [used in main] [renamed to I] */
  35. /*! export multiply [provided] [unused] [renamed to J] */
  36. /*! runtime requirements: __webpack_exports__ */
  37. /***/ ((__unused_webpack_module, exports) => {
  39. var __webpack_unused_export__;
  40. exports.I = function add() {
  41.     var sum = 0,
  42.         i = 0,
  43.         args = arguments,
  44.         l = args.length;
  45.     while (i < l) {
  46.         sum += args[i++];
  47.     }
  48.     return sum;
  49. };
  51. __webpack_unused_export__ = function multiply() {
  52.     var product = 0,
  53.         i = 0,
  54.         args = arguments,
  55.         l = args.length;
  56.     while (i < l) {
  57.         sum *= args[i++];
  58.     }
  59.     return sum;
  60. };
  63. /***/ })
  64. /******/     ]);
  65. /************************************************************************/
  66. /******/     // The module cache
  67. /******/     var __webpack_module_cache__ = {};
  68. /******/
  69. /******/     // The require function
  70. /******/     function __webpack_require__(moduleId) {
  71. /******/         // Check if module is in cache
  72. /******/         if(__webpack_module_cache__[moduleId]) {
  73. /******/             return __webpack_module_cache__[moduleId].exports;
  74. /******/         }
  75. /******/         // Create a new module (and put it into the cache)
  76. /******/         var module = __webpack_module_cache__[moduleId] = {
  77. /******/             // no module.id needed
  78. /******/             // no module.loaded needed
  79. /******/             exports: {}
  80. /******/         };
  81. /******/
  82. /******/         // Execute the module function
  83. /******/         __webpack_modules__[moduleId](module, module.exports, __webpack_require__);
  84. /******/
  85. /******/         // Return the exports of the module
  86. /******/         return module.exports;
  87. /******/     }
  88. /******/
  89. /************************************************************************/
  90. (() => {
  91. /*!********************!*\
  92.   !*** ./example.js ***!
  93.   \********************/
  94. /*! unknown exports (runtime-defined) */
  95. /*! runtime requirements: __webpack_require__ */
  96. const inc = __webpack_require__(/*! ./increment */ 1)/* .increment */ .nP;
  97. var a = 1;
  98. inc(a); // 2
  100. })();
  102. /******/ })()
  103. ;