第二篇ts，es6箭头函数结合typescript,和for...of

1.基本用法:

 const f = v => v
 // 等同于
 const f = function(v) {
    return v
 }

2.箭头函数返回数组

    const f = () => {
      const list = [1,2,3]
      // 直接返回一个对象
      return list.map(it => ({
        id: it
      }))
    }

    const result = f() // [{id:1},{id:2},{id:3}]

3.箭头函数和变量解构结合使用

  const full = ({first,last}) => `${first}_${last}`
  // ? 实现可选参数的功能
  const full = (first:string,last?: string) => `${first}_${last}`
  const full = (first:string,last="smith") => `${first}_${last}`
  // 剩余参数
  const full = (first:string,...restOfName: string[]) =>  {
      return first + " " + restOfName.join(" ");
    }
}

}   

4.箭头函数结合默认值

    const full = ({first,last}={first:'Mrs',last:'Right'})=> `${first}_${last}`

5.箭头函数结合typescript

const full = ( params: { first: string; last: string } )=> {
        const {first,last } =params
        return `${first}_${last}`
    }

for…of循环

 const list = ['a','b','c']
 for(let val of list) {
   console.log('val', val)
  }
  
 const listObj = [{name:'a'},{name:'b'},{name:'c'}]
  for(let {name: item} of listObj) {
      console.log('name', item)
 }
    
  // a,b,c
 // 区分for...in
  for(let num in list) {
     console.log('num', num)
  }
    // 0,1,2

在单页运用的项目，箭头函数是最常用的，也是简洁的。