• js闭包??


    <script>
         var name = "The Window";
         var object = {
        name : "My Object",
    
        getNameFunc : function(){
                                console.log("11111");
                                console.log(this);  //this == object  //调用该匿名函数的是对象
          return function(){
                                  console.log("22222");
                                  console.log(this); //this == window   //匿名函数下的匿名函数
          return this.name;
          };
        }
    
      };
      alert(object.getNameFunc()());
            
            
            //--
      var name = "The Window";
    
      var object = {
        name : "My Object",
    
        getNameFunc : function(){
          var that = this;
          return function(){
                          console.log("33333");
                           console.log(this); //this==window
                          console.log("44444");
                           console.log(that); //that==object
            return that.name;
          };
    
        }
    
      };
    
      alert(object.getNameFunc()());
        </script>
    function makeFunc() {
        var name = "Mozilla";
        function displayName() {
            alert(name);
        }
        return displayName; //返回一个函数
    }
    var myFunc = makeFunc(); //把函数返回值赋值给myFunc
    console.log(myFunc); //输出函数内容
    myFunc();//调用函数
    function makeAdder(x) {
        return function (y) { //返回一个函数
            return x + y; //返回值
        };
    }
    var add4 = makeAdder(); //无传参函数返回值
            console.log("//无传参函数返回值");
            console.log(add4);//输出函数体
            console.log(add4(2)); //NaN  Number.NaN 是一个特殊值,说明某些算术运算(如求负数的平方根)的结果不是数字
            
    var add5 = makeAdder(5); //把函数返回值赋值给add5,
            console.log("//有参函数返回值");
            console.log(add5);//输出函数体
             console.log(add5(2));//7
        var Counter1 = (function () { })();
        console.log("输出立即调用函数返回值Counter1");
        console.log(Counter1); //undefined
        var Counter2 = (function () { var privateCounter = 0; })();
        console.log("输出立即调用函数返回值Counter2");
        console.log(Counter2); //undefined
        var Counter3 = (function () {
            var privateCounter = 0;
            function changeBy(val) {
                privateCounter += val;
            }
    
        }
        )();
        console.log("输出立即调用函数返回值Counter3");
        console.log(Counter3); //undefined    
        //--
        var Counter4 = (function () {
            var privateCounter = 0;
            function changeBy(val) {
                privateCounter += val;
            }
            return {
                value: function () {
                    return privateCounter;
                }
            }
        }
        )();
        console.log("输出立即调用函数返回值Counter4");
        console.log(Counter4); //{value: ƒ} //类型object
    var Counter = (function () {
        var privateCounter = 0;
        function changeBy(val) {
            privateCounter += val;
        }
        return {
            increment: function () {
                changeBy(1);
            },
            decrement: function () {
                changeBy(-1);
            },
            value: function () {
                return privateCounter;
            }
        }
    })();
    console.log(Counter.value()); /* logs 0 */ //返回0
    Counter.increment(); //执行0+1
    Counter.increment(); //执行1+1
    console.log(Counter.value()); /* logs 2 */ //输出2
    Counter.decrement(); //执行2+(-1)
    console.log(Counter.value()); /* logs 1 */ //输出1

     https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Closures

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  • 原文地址:https://www.cnblogs.com/enych/p/8966592.html
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