js函数的调用和表达式

September 28, 2018

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JS函数的表达式

    //函数的表达式
    var c=(function(a,b){console.log( a+b);})

    var f=function ff(){};

    var f=function fact(x){
        if(x<=1){
            return 1;
        }else{
            return x * fact(x-1);
        }
    }
    console.log(f(5));

    var f=function (x){
        if(x<=1){
            return 1;
        }else{
            return x * arguments.callee(x-1);
        }
    }
    console.log(f(5));

    function f1(xingcan){
        //如果函数没有返回值、那么返回undefined
        console.log(xingcan);
        console.log(xingcan());
    }
    //f2()是函数声明
    function f2(){
        console.log("I am f2()");
        return "f2 say hello1";
    }
    f1(f2);

JS函数的调用

<script>
    //函数的调用
    //1.函数的调用方式
    (function (){console.log(12);})();
    //函数立即执行
    (function (x){ console.log(x+"喜欢美女");})("东哥");

    
    (function f(x){
        console.log(x); return x;
    })(4);
    (function(y){
        console.log(y);  return y;
    }(6));



    function add(a,b){
        return a+b;
    }
    console.log(add(1,1));
    //2.函数做为方法调用
    var obj={
        add:function(a,b){
            return a+b;
        }
    }

    var obj1={};
    obj1.add=function(a,b){
        return a+b;
    }

    var obj2={};
    function add(a,b){
        return a+b;
    }

    obj2.add=add;

    console.log(obj.add(1,2));
    console.log(obj1['add'](1,3));
    console.log(obj2.add(1,4));

    //3.构造函数
    var arr= new Array();
    //跟PHP一样实例化一个对象会自动调用构造函数

    //4.间接调用
    //间接调用和直接调用，唯一的区别就是可以绑定this指针
    //如果不考虑this,这三种调用方式完全一样
    function hypotenuse(a,b){
        return Math.sqrt(a *a + b*b);
    }
    console.log(this.hypotenuse(3,4));
    hypotenuse.call(this,3,4);
    hypotenuse.apply(this,[3,4]);

</script>

立即执行函数


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title&lt;/title>
</head>
<body>
<script src="http://www.bjpowernode.com/Public/home/public/header/js/jquery.min.js?v=1.12.2"></script>

<script>


    var clueContactRepeatIds = new Array();
    var a=5;
    (function ($,b,c,d) {
        console.log("我是 $ 开始 ");
        console.log($);
        console.log("我是 $ 结束 ");
        console.log("clueContactRepeatIds 等于 b ？" +(clueContactRepeatIds==b));
        console.log(c);
        console.log(d);
    })(jQuery,clueContactRepeatIds,a);

</script>

</body>
</html>

<script>


    var clueContactRepeatIds = new Array();
    var a=5;
    (function ($,b,c,d) {
        console.log("我是 $ 开始 ");
        console.log($);
        console.log("我是 $ 结束 ");
        console.log("clueContactRepeatIds 等于 b ？" +(clueContactRepeatIds==b));
        console.log(c);
        console.log(d);
        function sayHello() {alert("hello world");}
        function sayByeBye(){alert("Bye Bye~!");} //弹出bye bye。
        sayByeBye();
    })(jQuery,clueContactRepeatIds,a);

        sayHello(); //没有被弹出、立即执行函数、执行过后函数内被摧毁。所以sayHello不会出现
</script>

js函数的调用和表达式