使用类在对象实例化中指定属性分配

Question

假设我有一堂课

class Something {
  constructor(a, b) {
    this.a = a;
    this.b = b;
  }
}

我怎样才能实例化一个对象，以便我只给b赋值而不给a赋值？

例如类似于：

let someObject = new Something(b : 10);

预期输出：

log(someObject.a) // undefined
log(someObject.b) // 10 

出于代码可读性的原因，如果可以的话，我想避免使用let someObject = new Something(undefined, 10);。

我对 js 有点陌生，我不确定这是否可能，但任何帮助或指导将不胜感激！

Answer 1

你可以这样做：

class Something{
  // private properties don't even work in Firefox and the syntax is just more typing than constructors
  constructor(b, a){
    this.a = a;
    this.b = b;
  }
}
const something = new Something(10);
console.log(something);

但我会这样做：

function Something(b, a){
  let see = 'Wow these private varibles are really easy to use in costructors! Classes are lame!';
  this.a = a; this.b = b;
}
const something = new Something(10);
console.log(something);

阅读您的评论后：

function Something(){
  this.objects = [].slice.call(arguments);
  this.getObjIndex = obj=>{
    return this.objects.indexOf(obj);
  }
  this.getObjByIndex = index=>{
    return this.objects[index];
  }
}
const objTest1 = {test:1}, objTest2 = {test:2}, objTest3 = {really:'cool', why:['a', 2, 'z']};
const something = new Something(objTest1, objTest3);
console.log(something.objects);
console.log(something.getObjIndex(objTest3));
console.log(something.getObjByIndex(0));

@VLAZ 有这么多 cmets（顺便说一句，我对此没有任何问题），我必须展示私有变量：

function PrivateTest(){
  let test = 'cool';
  this.getTest = ()=>{
    return test;
  }
  this.setTest = mixed=>{
    test = mixed;
    return this;
  }
}
const pt = new PrivateTest;
console.log(pt.getTest());
console.log(pt.setTest('Look, VLAZ, it works!').getTest());