js精要之函数

数组排序

　　var arr = [1,6,3,5,7,2];
    arr.sort(function(a,b){
        return a-b;
    });
    console.log(arr);

 arguments 参数存储对象

  function ref(value){
        return value;
    }
    console.log(ref("hi!"));
    console.log(ref("hi!",25));
    console.log(ref.length);
    ref = function(){
        return arguments[0];
    }
    console.log(ref("hi!"));
    console.log(ref("hi!",25));
    console.log(ref.length);

函数sum计算数据和

　　function sum(){
        var result = 0;
        for(var i=0;i<arguments.length;i++){
            result+= arguments[i];
        }
        return result;
    }
    console.log("sum() - "+sum());

// 类重载

 function showa(){
        if(arguments.length === 0){
            console.log("没有参数");
        }else if(arguments.length === 1){
            console.log("一个参数："+arguments[0]);
        }
    }
    showa();

字面形式对象调用公共方法

function sayNameForAll(){
        console.log(this.name)
    }
    var person1 = {
        name:"zs1",
        sayName:sayNameForAll
    }
    var person2 = {
        name:"ls2",
        sayName:sayNameForAll
    }
    var name = "ww3";
    person1.sayName();
    person2.sayName();
    sayNameForAll()

// call();参数1指定this的值，参数2 传给函数的参数

function sayNameForAlla(label){
        console.log(label+":"+this.name)
    }
    var person1a = {
        name:"zs1"
    
    }
    var person2a = {
        name:"ls2"
        
    }
    var name = "ccc"
    sayNameForAlla.call(this,"name")
    sayNameForAlla.call(person1a,"person1a")

// apply()

sayNameForAlla.apply(this,["namea"])
sayNameForAlla.call(person1a,["person1a"])

// 判断对象中是否含有属性 in (包括原型属性)

　　console.log("name" in person2a);    //true
    console.log("toString" in person2a); //true

 // 判断对象中是否含有属性 hasOwnProperty() (不包括 原型属性) toString()是所有对象都具有的原型属性

　　console.log(person2a.hasOwnProperty("name"));
    console.log(person2a.hasOwnProperty("toString"));
    // false

// delete 删除属性

    delete person1a.name;
    console.log("name" in person1a);