5種使JavaScript代碼庫更幹淨的方法

英文 | https://betterprogramming.pub/5-practices-to-make-your-javascript-code-base-cleaner-611300dfe088

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翻譯 | 楊小二

JavaScript無處不在，從PC端到移動裝置端，甚至是後端，都在使用JavaScript。

在本文中，我将嘗試一些可用來使代碼看起來更簡潔的實踐方案。

1、使用預設參數代替短路或條件

預設參數通常比短路更幹淨。

function SomeMethod(paramThatCanBeUndefined) {


   const localValue = paramThatCanBeUndefined || "Default Value";
   console.log(localValue)
   // ...
}
SomeMethod() // Default Value
SomeMethod("SomeValue") // SomeValue      

嘗試以下方法：

function SomeMethod(
  console.log(paramThatCanBeUndefined)
  // ...
}
SomeMethod() // Default Value
SomeMethod("SomeValue") // SomeValue      

聲明：Falsy值，如''，""，false，null，0，和NaN将不會被預設值替代：

function SomeMethod(paramThatCanBeUndefined = "Default Value") {        
  console.log(paramThatCanBeUndefined)  
  // ...
}
SomeMethod(null) // will not Default Value, will null Instead
SomeMethod("SomeValue") // SomeValue      

2、處理多個條件

const conditions = ["Condition 2","Condition String2"];
someFunction(str){
  if(str.includes("someValue1") || str.includes("someValue2")){
    return true
  }else{
    return false
  }
}      

一種更幹淨的方法是：

someFunction(str){
   const conditions = ["someValue1","someValue2"];
   return conditions.some(condition=>str.includes(condition));
}      

3、用動态鍵值對替換開關（即對象文字）

開關版本（或将開關替換為if / else）：

const UserRole = {
  ADMIN: "Admin",
  GENERAL_USER: "GeneralUser",
  SUPER_ADMIN: "SuperAdmin",
};
function getRoute(userRole = "default role"){




  switch(userRole){
    case UserRole.ADMIN:
      return "/admin"
    case UserRole.GENERAL_USER:
        return "/GENERAL_USER"
    case UserRole.SUPER_ADMIN:
        return "/superadmin"
    default:
      return "/" 
  }


}
console.log(getRoute(UserRole.ADMIN)) // return "/admin"
console.log(getRoute("Anything")) // return Default path
console.log(getRoute()) // return Default path
console.log(getRoute(null)) // return Default path


// More cases if new arrive
// You can think if else instead of switch      

動态鍵值對版本：

const UserRole = {
   ADMIN: "Admin",
   GENERAL_USER: "GeneralUser",
   SUPER_ADMIN: "SuperAdmin",
};
function getRoute(userRole = "default role"){
 const appRoute = {
  [UserRole.ADMIN]: "/admin",
  [UserRole.GENERAL_USER]: "/user",
  [UserRole.SUPER_ADMIN]: "/superadmin"
 };
 return appRoute[userRole] || "Default path";
}
console.log(getRoute(UserRole.ADMIN)) // return "/admin"
console.log(getRoute("Anything")) // return Default path
console.log(getRoute()) // return Default path
console.log(getRoute(null)) // return Default path
// No more switch/if-else here.
// Easy to Further expansion      

4、避免過多的函數參數

function myFunction(employeeName,jobTitle,yrExp,majorExp){
 return `${employeeName} is working as ${jobTitle} with ${yrExp}    years of experience in ${majorExp}`
}
//output be like John is working as Project Manager with 12 year of experience in Project Management
// you can call it via
console.log(myFunction("John","Project Manager",12,"Project Management"))
//    ***** PROBLEMS ARE *****
// Violation of 'clean code' principle
// Parameter sequencing is important
// Unused Params warning if not used
// Testing need to consider a lot of edge cases.      

這是一種更清潔的方法：

function myFunction({employeeName,jobTitle,yrExp,majorExp}){
 return `${employeeName} is working as ${jobTitle} with ${yrExp} years of experience in ${majorExp}`
}
//output be like John is working as Project Manager with 12 year of experience in Project Management
// you can call it via
const mockTechPeople = {
  employeeName:"John",
  jobTitle:"Project Manager",
  yrExp:12,
  majorExp:"Project Management"
}
console.log(myFunction(mockTechPeople))
// ES2015/ES6 destructuring syntax is in action
// map your desired value to variable you need.      

5、使用Object.assign設定預設對象

這看起來很繁瑣：

const someObject = {
 title: null,
 subTitle: "Subtitle",
 buttonColor: null,
 disabled: true
};
function createOption(someObject) {
 someObject.title = someObject.title || "Default Title";
 someObject.subTitle = someObject.subTitle || "Default Subtitle";
 someObject.buttonColor = someObject.buttonColor || "blue";
 someObject.disabled = someObject.disabled !== undefined ?  someObject.disabled : true;
 return someObject
}
console.log(createOption(someObject));


// Output be like 
// {title: 'Default Title', subTitle: 'Subtitle', buttonColor: 'blue', disabled: true}      

const someObject = {
  title: null,
  subTitle: "Subtitle",
  buttonColor: null,
  disabled: true
 };
 function creteOption(someObject) {
  const newObject = Object.assign({
   title: "Default Title",
   subTitle: "Default Subtitle",
   buttonColor: "blue",
   disabled: true
 },someObject)
 return newObject
 }
 console.log(creteOption(someObject));