首先聲明，不是要消除if
而是，減少一些不必要的if判斷，使得代碼更優雅，更重要的是提高可維護性

most easy

use Ternary:

var result = condiction? trueResult : falseResult;  

缺點：case 超過2個就不容易了

use switch

in static type language

• use heritance

usage (c++):

  SonClasss son = new FatherClass()
  son.doSomething()

in Son class

  protected void doSomething(){
    //here override the FatherClass implement
    print("I did something different from my father");
  }
 

• use polypeptide

in dynamic type language

also: you can use heritance way in class:

  //es5
  function Son(){};
  util.inherits(Son, Father);
  Son.prototype.doSomething(){
    console.log("I did something different from my father");
  }
  //usage:
  var son = new Son();
  son.doSomething();
 

  //es6 use extends
  //

in dynamic lange, your choice become something different and sometimes difficult

• use array

  //usage:
  //req.query = {"name":"Wade", "surname": "Deng"}
  SonClass son = new ClassFactory(req.query.name);
  son.doSomething();
  
  //ClassFactory implement   , if else hidden in ClassFactory
  function ClassFactory(name){
    this.name = name;
    this.subClass = name == "Wade" ? new subClass(name)  : new sub2Class(name);
  }
  
 

• use key-value json

SonClass.prototype.doSomething(actionName){
  var do = {
    'cry' :{ console.log('cry');}
    'eat' :{ console.log('eat');}
  }
  return do(actionName);
}

However , sometime reading a few if else statements is easy.

ref

[anti-if-else-patterns]（http://www.techug.com/anti-if-the-missing-patterns）
no more ifs alternatives
anti-anti-if

如何寫更少的 if else