function foo(){var something = 'cool';var another = [1, 2, 3];function doSomething() {console.log( something );}function doAnother() {console.log( another.join( " ! " ) );} } // 是一個不明顯的閉包,doSomething()和doAnother()保持了foo的內(nèi)部作用域

接下來考慮以下的代碼:

function CoolModule() {var something = "cool";var another = [1, 2, 3];function doSomething() {console.log( something );}function doAnother() {console.log( another.join( " ! " ) );}return {doSomething: doSomething,doAnother: doAnother}; }var foo = CoolModule();foo.doSomething(); // "cool" foo.doAnthor(); // 1!2!3 // 上述通過 return 將doSomething和doAnother暴露出來,在js中被稱為模塊.

從上面可以抽象出模塊模式所必須的兩個必要條件:
1.必須有外部的封閉函數(shù),該函數(shù)必須至少被調(diào)用一次(每次調(diào)用都會創(chuàng)建一個新的模塊實(shí)例)
2.封閉函數(shù)必須返回至少一個內(nèi)部函數(shù),這樣內(nèi)部函數(shù)才能在私有作用域中形成閉包,并且可以訪問或者修改私有的狀態(tài).

下面看一個單例模式:

var foo = (function CoolModule() {var something = 'cool';var another = [1, 2, 3,];function doSomething() {console.log( something );}function doAnother() {console.log( another.join( " ! " ) );}return {doSomething: doSomething,doAnother: doAnother} })(); foo.doSomething(); // cool foo.doAnother(); // 1!2!3// 注:上述的CoolModule在執(zhí)行一次后便釋放掉了.

接受參數(shù)的模塊:

functioin CoolModule(id) {function identify() {console.log( id );}return {identify: identify} }var foo1 = CoolModule( "foo 1" ); var foo2 = CoolModule( "foo 2" ); foo1.identify(); // "foo 1" foo2.identify(); // "foo 2"// 沒啥好說的...

現(xiàn)代的模塊機(jī)制

var MyModules = (function Manager() {var modules = {};function define(name, deps, impl) {for (var i=0; i < deps.length; i++) {deps[i] = modules[deps[i]];}modules[name] = impl.apply( impl, deps );}function get(name) {return modules[name];}return {define: define,get: get}; })();// 上述定義了一個模塊依賴加載器/管理器,下面使用上述的函數(shù)來定義模塊 MyModules.define( " bar" , [], function() {function hello(who){return "Let me introduce: " + who;}return {hello: hello} }); MyModules.define( " foo ", ["bar"], function(bar) {var hungry = "hippo";function awesome() {console.log( bar.hello( hungry ).toUpperCase() );}return {awesome: awesome}; }); var bar = MyModules.get( "bar" ); var foo = MyModules.get( "foo" );console.log(bar.hello( "hippo" ) ); // Let me introduce: hippofoo.awesome(); // LET ME INTRODUCE: HIPPO

ES6中的模塊

// bar.js function hello(who) {return "Let me introduce: " + who; } export hello;// foo.js import hello from "bar";var hungry = "hippo";function awesome() {console.log(hello( hungry ).toUpperCase()); } export awesome;// baz.js import foo from "foo"; // 書上是module foo from "foo" import bar from "bar";console.log(bar.hellow( "rhino" ) ); // Let me introduce: rhinofoo.awesome(); // LET ME INTRODUCE: HIPPO

ES6模塊和CommonJS模塊的差異:
https://blog.csdn.net/piano9425/article/details/89946163

參考《你不知道的JavaScript》(上卷)P53~P56

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