优雅条件判断

用 return 替代 if - else

场景：互斥的条件判断

function test(data){
     let result = '';
     if(data<10){
         result = 'if'
     }else{
         result = 'else'
     }
     return result 
 }

==优化成==>

 function test(data){
    let result = '';
    if(data<10){
      return result = 'if'
    }
    return result = 'else'
}

使用 Array 的 includes 方法

场景：多种条件对应相同的处理

function region(province){
 let result = ""
   if(province === "广东"|| province === "广西"|| province === "福建" || province === "浙江" || province === "云南")  
   {
       result = "南方"
   }
   if(province === "河北"|| province === "黑龙江"|| province === "辽宁" || province === "山东" || province === "吉林")  
   {
       result = "北方"
   }
 }

==优化成==>

 function region(province){
     let result = ""
     let northProvinceArr = ["河北","黑龙江","辽宁","山东","吉林"]
     let southProvinceArr = ["广东","广西","福建","浙江","云南"]
     if(southProvinceArr.includes(province)) result = "南方";
     if(northProvinceArr.includes(province)) result = "北方"
 }

策略模式

场景：并列的多条件判断

function permission(role){
    if(role === “operations”){
        getOperationPermission()
    }else if(role === "admin"){
        getAdminPermission()
    }else if(role === "superAdmin"){
        getSuperAdminPermission()
    }else if(role === "user"){
       getUserPermission() 
    }
  }
// 或者下面这样
function permission(role){
      switch(role){
          case "operations": {
              getOperationPermission();
              break;
          }
          case "admin": {
              getAdminPermission();
              break;
          }
          case "superAdmin": {
              getSuperAdminPermission();
              break;
          }
          case "user": {
              getUserPermission();
              break;
          }
      }
  } 

==优化成==>

function permission(role){
       const actions = {
           operations: getOperationPermission,
           admin: getAdminPermission,
           superAdmin: getSuperAdminPermission,
           user: getUserPermission,
       }
       actions[role].call()
  }