Use of JS objects

This time I will bring you the use of JS objects. What are the precautions when using JS objects. The following is a practical case, let’s take a look.

1. Definition of object

Object:

    - 是复合类型，由简单数据类型和复合数据类型组成的。
    - 由一对{ }包起来的，
    - 0对或者多对 键名和键值 组成的对,
    - 每对键值对 之间用","隔开，最后一个不要加","

2. Creation of object

Method 1: Through ConstructorCreate object

• new Object();

Method 2 : Object literal creates an object

• { };

3. Add or modify attributes for the object

Method 1: Pass"."

<script>
    //通过构造函数创建对象
    var obj= new Object();
    //为对象添加属性
    obj.a=2;
    console.log(obj);//{a: 1}
    
    //通过对象字面量创建对象
    var t={};
    //为对象添加属性
    t.a=2;
    console.log(t);//{a: 1}    
</script>

Method 2:"[ ]"

<script>
    //通过构造函数创建对象
    var obj= new Object();
    //为对象添加属性
    obj.["a"]=2;
    console.log(obj);//{a: 1}
    
    //通过对象字面量创建对象
    var t={};
    //为对象添加属性
    t.["a"]=2;
    console.log(t);//{a: 1}    
</script>

Method 3: Write directly inside

<script>
    var obj= {
            name: "k",
            age: 12,
            gender: "male"
        }
     console.log(obj);//{name: "k", age: 12, gender: "male"}
</script>

4. Obtaining attribute values

Obtaining object values

- 方式一：对象.键名(属性名);
- 方式二：对象["键名"];

5.Using in and for in

Use of in:

  属性名 in 对象名
      检测 在 对象中 是否 含有此属性名。

eg:

<script>
    var obj={
        name:"L";
        age:22;
    };
    console.log(age in obj);//true
    console.log(gender in obj);//false
</script>

Use of for in:

Traversal All properties within object feel like a cycle.

<script>
        var obj={
                name:"k",
                age:21,
                gender:"women"
        };
        // i是指对象的属性名，会遍历对象的属性值。
        for (var i in obj){
            console.log("第"+i+"项的属性值为："+obj[i]);
        }
        var attr=[1,2,3,4];
        for (var i in attr){
            console.log("第"+i+"项值为："+attr[i]);
        }
</script>

The screenshot of the result is:

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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