ES5.6 常用新特性

1. let & const

定义变量使用let

for(let i=0; i<5; i++) {
      console.log(i);
  }
console.log("外"+i);

定义常量使用const

const j=0;
j=2;

2. 字符串的操作

1. includes、startwith、endwith
   
2. 字符串模板
   

3. 解构表达式

1. 解构数组
   .
2. 解构对象
   

4.函数优化

1. 函数参数默认值

   function fun1(a,b = 1) {
       // if(!b) {
       //     b = 1;
       // }
       // b = b || 1;
       console.log(a/b);
   }
   fun1(10);
   

2. 箭头函数

   let fun2 =a => {
       a = 1000;
       console.log(a);
   }
   fun2(10);
   
   let fun3 = (a,b=2) => {
       console.log(a/b);
   }
   fun2(10)
   

3. 对象内方法

   let person = {
       name: "そら",
       eat: function(food) {
           console.log(this.name+"吃了"+food);
       },
       eat1: food => console.log(person.name+"吃了"+food),
       eat2(food) {//常用
           console.log(this.name+"吃了"+food);
       }
   
   }
   person.eat("香蕉");
   person.eat("苹果");
   person.eat("梨");
   

4. 解构形参

   let p = {
      name: "小芳",
       age: 1
   }
   // let fun3 = (p1) => console.log(p1.name);
   let fun3 = ({name}) => console.log(name);
   fun3(p);
   

4.map和reduce

1. map

   let arr = [10,20,30];
   > undefined
   arr.map(a => a * 10)
   > (3) [100, 200, 300]
   let persons=[{name: "zhangsan",age: 1}, {name: "lisi",age:2}];
   > undefined
   persons.map(p => p.name)
   > (2) ["zhangsan", "lisi"]
   

2. reduce

   let arr = [10,20,30];
   arr.reduce((a,b) => a+b)
   > 60
   arr.reduce((a,b) => a+b, 100)
   > 160
   

5. 对象扩展

6.数组扩展

• find(callback)、findIndex(callback)、includes(数组元素)

let arr = [10,20,30,40,50]
> undefined
arr.find(a => a==40)
> 40
let persons=[{name: "zhangsan",age: 1}, {name: "lisi",age:2}];
> undefined
persons.find(p => p.age == 2)
> {name: "lisi", age: 2}
persons.findIndex(p => p.age==2)
> 1
arr.includes(60)
> false