javaScript的基本优雅写法

1.判断为空

小白：

if(a == undefined) a = [];
if(params.success){
  params.success(res);  
}

优雅：

a = a || [];
params.success&&params.success(res);

2.多条件判断

小白：

    var Statistics = function() {
      console.log('执行')
    }
    switch (currentTab){
      case 0:
        Statistics();
        break;
      case 1:
        Statistics();
        break;
      case 2:
        Statistics();
        break;
      case 3:
        Statistics();
        break;      
    }

优雅：

 var Statistics = function () {
      console.log('执行')
    }
    const comparativeTotles = new Map([
      [0,Statistics],
      [1,Statistics],
      [2,Statistics],
      [3,Statistics]
    ])
    let map = function(val: any){
      return comparativeTotles.get(val)
    }
    let getMap = map(4)
    if(!getMap){
      console.log('差找不到')
    }else{
      console.log('执行操作')
      getMap()
    }

3.if else

小白：

const onButtonClick = (status: any, identity: any) => {
      if (identity == 'guest') {
        if (status == 1) {
          console.log('do something')
        } else if (status == 2) {
          console.log('do something')
        } else if (status == 3) {
          console.log('do something')
        } else if (status == 4) {
          console.log('do something')
        } else {
          console.log('do something')
        }
      } else if (identity == 'master') {
        if (status == 1) {
          console.log('do something')
        } else if (status == 2) {
          console.log('do something')
        } else if (status == 3) {
          console.log('do something')
        } else if (status == 4) {
          console.log('do something')
        } else {
          console.log('do something')
        }
      }
    }

优雅：

const functionA = () => { /*do sth*/}
    const functionB = () => { /*do sth*/}
    const functionC = () => { /*send log*/}
    const actions = new Map([
      ['guest_1', () => { functionA }],
      ['guest_2', () => { functionB }],
      ['guest_3', () => { functionC }],
      ['guest_4', () => { functionA }],
    ])
    const onButtonClick = (identity, status) => {
      let action = actions.get(`${identity}_${status}`) || actions.get('default')
      action.call(this)
    }

 4.一些场景

//生成随机ID
Math.random().toString(36).substring(2);

//金钱格式化
var test1 = '1234567890'
var format = test1.replace(/\B(?=(\d{3})+(?!\d))/g, ',')
function formatCash(str) {
  return str.split('').reverse().reduce((prev, next, index) => {
    return ((index % 3) ? next : (next + ',')) + prev
})  
}