5种方法告诉你如何使JavaScript 代码库更干净

• 5、使用object.assign设置默认对象

1、使用默认参数代替短路或条件

默认参数通常比短路更干净。

function somemethod(paramthatcanbeundefined) {

   const localvalue = paramthatcanbeundefined || "default value";
   console.log(localvalue)
   // ...
}
somemethod() // default value
somemethod("somevalue") // somevalue

尝试以下方法：

function somemethod(
  console.log(paramthatcanbeundefined)
  // ...
}
somemethod() // default value
somemethod("somevalue") // somevalue

声明：falsy值，如''，""，false，null，0，和nan将不会被默认值替代：

function somemethod(paramthatcanbeundefined = "default value") {        
  console.log(paramthatcanbeundefined)  
  // ...
}
somemethod(null) // will not default value, will null instead
somemethod("somevalue") // somevalue

2、处理多个条件

const conditions = ["condition 2","condition string2"];
somefunction(str){
  if(str.includes("somevalue1") || str.includes("somevalue2")){
    return true
  }else{
    return false
  }
}

一种更干净的方法是：

somefunction(str){
   const conditions = ["somevalue1","somevalue2"];
   return conditions.some(condition=>str.includes(condition));
}

3、用动态键值对替换开关（即对象文字）

开关版本（或将开关替换为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

动态键值对版本：

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、避免过多的函数参数

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.

这是一种更清洁的方法：

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设置默认对象

这看起来很繁琐：

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}

这种方法看起来更好：

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));

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