Introduction to the basics of JavaScript_object (must read) (graphic tutorial)

Now I will bring you a basic introduction to JavaScript_object. Let me share it with you now and give it as a reference for everyone.

The base class of all Object classes

var obj = new Object();
var obj = {}; //实例化对象

There are two types of setting properties for objects:

1 .Use direct quantities: object.properties/methods, this method is intuitive and easy to understand

obj.name = '张三';
obj.age = 20;
obj.sex = '男';
obj.say = function(){
alert("hello World");
}

2.Use "[]": object.['properties/methods '], when using this method, "" or '' must be added within the brackets, the method is strict

obj['birthday'] = '1989-08-07';

获取对象的属性或者方法:对象.属性名/方法
alert(obj.name); // 张三
alert(obj.age); // 20
obj.say(); // hello World

delete 操作符 删除对象的属性或方法的
delete obj.age;
delete obj.say;
alert(obj.age);  //undified
alert(obj.sex);  //20
obj.say();   //报错，函数已被删除

Traverse a js object, for in statement

for(var attr in obj){
alert(attr + ":" + obj[attr]); //会按顺序将数组中的键值对打印，主要值，如果用对象.属性得到undified
}

Constructor saves the creation function of the object

alert(obj.constructor);
var o = [];
alert(o.constructor);

hasOwnProperty(propertyName) 用于检测给定属性在对象中是否存在,返回boolean类型，在项目中有时会用到，需留意
var i = {};
i.sex = '男';
alert(i.hasOwnProperty('sex')); //true
alert(i.hasOwnProperty('age')); //false

propertyIsEnumerable(propertyName)检测给定的属性是否能被for in 所枚举出来，返回boolean 
alert(i.propertyIsEnumerable('age')); //false 上面没有定义此属性

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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