ES6-对象优化

1】es6给Object扩展了许多新的方法，如

• key(obj)：获取对象的所有key形成的数组
• value(obj):获取对象的所有value形成的数组
• entries(obj):获取对象所有的key和value形成的二维数组

  const person = {
      name: "qiyue",
      age: 23,
      language: ["java", "js", "css"]
    }
    console.log(Object.keys(person)) //["name","age","language"]
    console.log(Object.values(person)) // ["qiyue",23,Array(3)]
    console.log(Object.entries(person)) //[Array(2),Array(2),Array(2)]

 

2】Object.assign方法的第一个参数是目标对象，后面的参数都是源对象；将源对象的属性赋值到目标对象中

    onst target = { a: 1 }
    const source1 = { b: 2 }
    const source2 = { c: 3 }
    Object.assign(target, source1, source2);
    console.log(target) //{a: 1, b: 2, c: 3}

 

3】声明对象简化

    //以前
    const name = 'sanyue'
    const age = 21
    //将属性值name，age分别赋给person1对象的name，age,后面是属性值
    const person1 = { name: name, age: age }
    console.log(person1) //{name: "sanyue", age: 21}

    //es6:属性名和属性值变量名一样，可以省略
    const person2 = {name,age}
    console.log(person2) //{name: "sanyue", age: 21}

 

4】对象函数属性简写

 let person3 = {
      name: "qiyue",
      //以前
      eat: function (food) {
        console.log(this.name + "在吃" + food);
      },
      //箭头函数中this不能使用，用对象.属性
      eat2: food => console.log(person3.name + "在吃" + food),
      eat3(food) {
        console.log(this.name + "在吃" + food)
      }
    }
    person3.eat("苹果") //qiyue在吃苹果
    person3.eat2("香蕉") // qiyue在吃香蕉
    person3.eat3("西瓜") //qiyue在吃西瓜

 

5】对象扩展运算符

    //拷贝对象（深拷贝）
    let p1 = { name: "qiyue", age: 23 }
    let obj = { ...p1 }
    console.log(obj)//{name: "qiyue", age: 23}

    //合并对象
    let age1 = { age: 24 }
    let name1 = { name: "qiyue" }
    let p2 = {}
    p2 = { ...age1, ...name1 }
    console.log(p2) //{age: 24, name: "qiyue"}
    //如果p2中原本有name,age属性会被覆盖