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);