js匿名函数和闭包

//普通函数function box() {return 'Lee';}alert(box());//匿名函数function () {//单独的匿名函数，是无法运行的return 'Lee';//就算能运行，也无法调用，因为没有名称}//把匿名函数赋值给变量var box = function () {return 'Lee';};alert(box());//通过自我执行来执行匿名函数(function () {//(匿名函数)();第一圆括号放匿名函数，第二个圆括号执行alert('Lee');})();(function () {alert('Lee');})();//把匿名函数自我执行的返回值赋给变量var box = (function () {return 'Lee';})();alert(box);//自我执行后用alert()打印alert((function () {return 'Lee';})());//自我执行匿名函数的传参(function (age) {alert(age);})(100);//函数里放一个匿名函数function box() {return function () {// 闭包return 'Lee';}}alert(box()());function box() {return function () {// 闭包return 'Lee';}}var b = box();alert(b());//通过闭包返回局部变量function box() {var age = 100;return function () {return age;};}alert(box()());//使用全局变量进行累加var age = 100;function box() {age++;}alert(age);box();alert(age);box();alert(age);//使用局部变量进行累加function box() {var age = 100;age++;return age;}alert(box());alert(box());alert(box());alert(box());alert(box());//使用匿名函数实现局部变量驻留内存中从而累加function box() {var age = 100;return function () {age++;return age;};}var b = box();alert(b());alert(b());alert(b());alert(b());//alert(age);b = null;//解除引用，等待垃圾回收alert(b());//循环里的匿名函数的取值问题function box() {var arr = [];for (var i = 0; i < 5; i ++) {arr[i] = function () {//arr[0] = 0，arr[1] = 1 .... arr[4]  = 4return i;};}//循环已经执行完毕了，i最终是4++ = 5 ,那么最终就是5return arr;}//alert(box()[0]);var b = box();//alert(b.length);for (var i = 0; i < 5; i ++) {alert(b[i]());}//改0function box() {var arr = [];for (var i = 0; i < 5; i ++) {arr[i] = i;}return arr;}var b = box();for (var i = 0; i < 5; i ++) {alert(b[i]);}//改1function box() {var arr = [];for (var i = 0; i < 5; i ++) {arr[i] = (function (num) {//通过自我及时执行匿名函数return num;})(i);}return arr;}var b = box();for (var i = 0; i < 5; i ++) {alert(b[i]);}//改2function box() {var arr = [];for (var i = 0; i < 5; i ++) {arr[i] = (function (num) {//num其实在这里return function () {//因为闭包可以将变量驻留在内存中，和上一节课的累加是一个道理return num;}})(i);}//已经执行完毕了，num为什么可以0,1,2,3,4return arr;}var b = box();for (var i = 0; i < 5; i ++) {alert(b[i]());}var b = function () {alert('Lee');}();function box() {var arr = [];for (var i = 0; i < 5; i ++) {arr[i] = function (num) {return function () {//因为闭包可以将变量驻留在内存中，和上一节课的累加是一个道理return num;}}(i);}//已经执行完毕了，num为什么可以0,1,2,3,4return arr;}var b = box();for (var i = 0; i < 5; i ++) {alert(b[i]());}//关于this对象var box = {getThis : function () {return function () {return this;}}};alert(box.getThis()());var user = 'The Window';var box = {user : 'The Box',getUser : function () {//这里作用域的this是Boxvar that = this;return function () {//这里作用域的this是windowreturn that.user;}}};//alert(box.getUser()());//对象冒充//alert(box.getUser().call(box));alert(box.getUser()());function box() {var oDiv = document.getElementById('oDiv');var text = oDiv.innerHTML;oDiv.onclick = function () {alert(text);};oDiv = null;//解除引用，等待垃圾回收alert(oDiv);}box();//块级作用域(私有作用域)function box() {for (var i = 0; i < 5; i ++) {//块级作用域(JS没这个东西)}alert(i);}box();function box() {for (var i = 0; i < 5; i ++) {//块级作用域(JS没这个东西)}var i = 111;//就算重新声明，也不会影响之前声明初始化的数据alert(i);}box();//使用块级作用域(私有作用域)function box() {(function () {//包含自我执行的匿名函数，就可以实现私有作用域for (var i = 0; i < 5; i ++) {alert(i);}// 这里面用了a,b,c等变量})();被销毁了//这里可以继续似乎用a,b,c等变量，和上面的a,b,c完全没有联系//出了这个私有作用域，变量立即被销毁alert(i);//这里就不认识了}box();//全局变量var age = 100;alert(age);age = null;//私有作用域来表示(function () {//这里就是全局的私有作用域var age = 100;alert(age);})();(function () {var a;var b;})()://私有变量function box() {var age = 100;//私有变量}box();function Box() {this.age = 100;//属性，公有的this.run = function () {//方法，公有的return '运行中...';};}var box = new Box();alert(box.age);alert(box.run());function Box() {var age = 100;//私有变量function run() {//私有函数return '运行中...';}this.publicGo = function () {//对外可见的公共接口，特权方法return age + run();};this.getAge = function () {return age;}}var box = new Box();alert(box.getAge());//通过构造函数传参function Box(value) {var user = value;//私有变量this.getUser = function () {return user;};}var box = new Box('Lee');alert(box.getUser());var box2 = new Box('kkk');alert(box.getUser());function Box(value) {var user = value;//私有变量this.getUser = function () {return user;};this.setUser = function (value) {user = value;}}var box = new Box('Lee');alert(box.getUser());box.setUser('OOO');alert(box.getUser());function Box(value) {var user = value;//私有变量this.getUser = function () {return user;};this.setUser = function (value) {user = value;}}var box = new Box('Lee');alert(box.getUser());var box2 = new Box('kkk');alert(box.getUser());(function () {var user = ''//私有变量//function Box() {}//构造函数，但在函数里写构造函数，不支持，因为私有作用域里的函数，外部无法访问Box = function (value) {//全局，构造函数user = value;};Box.prototype.getUser = function () {return user;};Box.prototype.setUser = function (value) {user = value;}})();var box = new Box('Lee');//第一次实例化alert(box.getUser());var box2 = new Box('kkk');//第二次实例化alert(box.getUser());box2.setUser('OOO');alert(box.getUser());//什么叫单例，就是永远只实例化一次，其实就是字面量对象声明方式var box = {//第一次实例化，无法第二次实例化，那么就是单例user : 'Lee',run : function () {return '运行中..';}};var box = function () {var user = 'Lee';//私有变量function run() {//私有函数return '运行中...';}return {publicGo : function () {//对外公共接口的特权方法return user + run();}};}();alert(box.publicGo());var box = function () {var user = 'Lee';//私有变量function run() {//私有函数return '运行中...';}var obj =  {publicGo : function () {//对外公共接口的特权方法return user + run();}};return obj;}();alert(box.publicGo());//之前两个，都是返回的{} 也就是Object，那么我想返回自定义的呢？Box，Deskfunction Desk() {}var box = function () {var user = 'Lee';//私有变量function run() {//私有函数return '运行中...';}var desk = new Desk();desk.publicGo = function () {return user + run();};return desk;}();alert(box.publicGo());