js object.create()、Object.defineproperty()、,Object.keys()...for..in,for..each

本文链接：https://blog.csdn.net/java_goodstudy/article/details/68954997

本文深入探讨了JavaScript中创建对象的方法，包括使用构造函数、Object.create()及Object.defineProperty等技术细节。并通过实例展示了如何利用这些方法定义对象属性及其可枚举性。

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Speak of that how to create object in javascript , maybe you know:

Object.keys() : return array of object attribute that can't be enumerable

new Object();
var obj = {};
new function(){}; // var obj = new function(){}();

Have you know Object.create()?

这里写图片描述

//as the photo you needn’t to care all is object and proto all assign Object , you can read somethind else

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Accord to above , you know when you new a obj , that is ,the obj proto will have a constructor assign object .

Note: you can use construtor.prototype ={} , to set obj proto assign , but this can’t be used in where object.

Object.create() ; default param

    {
        //http://www.jb51.net/article/77039.htm
        //http://blog.csdn.net/sinat_22996989/article/details/49559513
        // the consructor need return undifined but obj otherwise will get the new obj thar you reurn
        function cons(){
            let args = Array.prototype.slice.call(arguments);
            this.name = args[0];
            this.love = args[1];
            this.say =()=>console.log(this.name);
            this.play=()=>console.log(this.love)
        }

        let o = new cons(`qi`,`play game`);



        // you can create obj base on null just like object.create(null,{propertiesObject});
        var obj = Object.create(o,{
            nickName:{
                value:'kongdaluoli',
            },
        });

        //check can enmu
        for(let key in obj){
            console.log(`check out the obj key is ${key}`);
        }

        window.oo = obj;

        var d= {};
        d.prototype.say=function () {
            console.log("sb")
        }


        //new a obj then use prototype

    }```

   //enumerable: false
   //configurable: false
   //writable: false

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so, when you use for…in will get : (not found nickName attribute)

Object.defineProperty

Note :use Object.defineProperty if you have used writable or value before will not set the function of set and get at the same time, you can use it for obj exit attribute or add new attribute . it’s convenient that use Object.defineProperties to define multiple attribute .

     function cons(){
                let args = Array.prototype.slice.call(arguments);
                this.name = args[0];
                this.love = args[1];
                this.say =()=>console.log(this.name);
                this.play=()=>console.log(this.love)
            }

        let o = new cons(`qi`,`play game`);


        // you can create obj base on null just like object.create(null,{propertiesObject});
        var obj = Object.create(o,{
            nickName:{
                value:'kongdaluoli',
            },
        });

        Object.defineProperty(obj,"wanna",{
            value:"want back",
            configurable:false,
        })


            //if you have set someone attribute configurable:false , will not set the descriptor again
    //        Object.defineProperty(obj,"wanna",{
    //            value:"want back",
    //            configurable:false,
    //            enumerable:true,
    //        })


     Object.defineProperty(obj,"wanna1",{
                value:"want back",
                configurable:false,
                enumerable:true,
            })

        Object.defineProperties(obj,{
            pros:{
                value : 123,
                enumerable:true,
            },
            pros1:{
                value : 1234,
            },
        })
        //check can enmu
        for(let key in obj){
            console.log(`check out the obj key is ${key}`);
        }

        window.oo = obj;