Detailed examples of CommonJS

1. CommonJS

• is used for server-side modular programming. For example, nodejs adopts this specification;

• A file is a module , the require method is used to load modules. This method reads a file and executes it, and finally returns the module.exports object inside the file;

• require reads .js files by default, so require (module name) does not need to be written with a suffix;

• is loaded synchronously. Since the modules loaded on the server side are generally local, this is OK; but on the client side, if a module is too large, Will cause the page to "fake death";

• The module.exports attribute represents the external output interface of the current module. When other files load the module, they actually read the module.exports variable; for convenience, You can use exports, exports points to module.exports; that is, exports = module.exports = {}

• exports.xxx is equivalent to adding an attribute to the exported object, which is visible to the calling module ;

• exports = is equivalent to reassigning exports, which cuts off the association with module.exports, and the calling module cannot access the exports object and its properties;

2. AMD

• Load module: require([module], function(module){});

• Define module: define([module], function(module){}); module is a dependent module;

• ##require.js (a tool library for front-end modular management) implements js files Asynchronous loading prevents web pages from losing response; managing dependencies between modules facilitates code writing and maintenance.

• Dependency pre-positioning, execute module dependency blocks as early as possible, the execution order is not necessarily 1 first and then 2;

• Load non-standard modules

  require.config({
      baseUrl: "js/lib",
      paths: {"jquery": "jquery.min",
  　　  "underscore": "underscore.min",
  　　  "backbone": "backbone.min"　 },
      shim: {'underscore':{
              exports: '_'　　　},
  　　　'backbone': {
  　　　　deps: ['underscore', 'jquery'],
  　　　　exports: 'Backbone'　　　}
  　}
  });
  // exports值（输出的变量名），表明这个模块外部调用时的名称；deps数组，表明该模块的依赖性

3. CMD

define(function(require, exports, module){
    var a = require('a');
    a.foo();
};

• Sea.js

• The dependency is nearby, and the dependent module is executed only when the dependent module is really needed, and the order is fixed;

• The biggest difference between AMD and CMD is the execution timing of the dependent module The processing is different, not the timing or method of loading. Both are loading modules asynchronously;

• AMD depends on the front-end, js can easily know who the dependent module is and load it immediately; and CMD depends on the nearest one. You need to use the module to be converted into a string and parsed to know which modules it depends on.

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