【JS-if】小技巧

带有if的代码简化

function validation(customer) {
  if (!customer.email) {
    return error('email is require')
  } else if (!customer.login) {
    return error('login is required')
  } else if (!customer.name) {
    return error('name is required')
  } else {
    return customer;
  }
}

重构后的代码

const customerValidation = customer =>
  !customer.email   ? error('email is required')
  : !customer.login ? error('login is required')
  : !customer.name  ? error('name is required')
                    : customer ;

短路运算符1

if(name){
	login(name) //执行
}

重构

name&&login(name);

短路运算符2

if(name&&password){
	login(name,password) //执行
}

重构后

var name = true;
var password = '001'
function login(name,password){
  console.log('登录成功')
}
name&&password && login(name,password);

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swich的代码

var day;
switch (new Date().getDay()) {
  case 0:
    day = "周日";
    break;
  case 1:
    day = "周一";
    break;
  case 2:
    day = "周二";
    break;
  case 3:
    day = "周三";
    break;
  case 4:
    day = "周四";
    break;
  case 5:
    day = "周五";
    break;
  case  6:
    day = "周六";
}
console.log(day)

重构后

const nowWeek = (day) => ({
  '0':'周日',
  '1':'周一',
  '2':'周二',
  '3':'周三',
  '4':'周四',
  '5':'周五',
  '6':'周六',
})[day] || '其他'
var a = nowWeek(1);
console.log(a) //周一

// 例子一个函数返回一个对象
const aa = (day) => ({
  '0':'周一'
})
console.log(aa(0))
const bb = (day) => {
  return {
    '0':'周一'
  }
}
console.log(bb(0))