为Java类创建静态或类变量的现代方法 [英] Modern way to create static or Class variable for Javascript class

问题描述

我已经在寻找一个明确的答案，而且大部分的东西仍然与旧的（或者我应该说传统的）使用 function 。

根据此SO答案 ，

ES2015不支持类属性。

据我所知，向类添加静态变量的唯一方法就是：

https://jsfiddle.net/abalter/fknwx3n4/

  class C {
 
 constructor（x）{
 console.log（in constructor+ x）; 
 this.x = x; 
 this.add（this.x）; 
} 
 
 add（x）{
 console.log（in add+ x）; 
 C.alist.push（x）; 
} 
 
 show（）{
 console.log（in show）; 
 console.log（C.alist）; 
} 
} 
 
 //必须在实际的类定义之外完成。 
 C.alist = []; 
 
 c1 = new C（5）; 
 c1.show（）; 
 c2 = new C（10）; 
 c1.show（）; 
 c2.show（）; 
  

这是故事的结尾吗？

解决方案

你可以调用一个静态函数来初始化所有的定义了类之后的静态成员，然后可选地删除该函数。 （可能重置静态变量将是一个功能？）

这将允许您将所有的静态变量保存在类声明中。 / p>

  class C {
 static init（）{
 C.alist = []; 
} 
 
构造函数（x）{...} 
 add（x）{...} 
 show（）{...} 
} 
 C.init（）; 
删除C.init; 
  

另一个选项是初始化构造函数中的静态变量，但这要求至少有一个对象被实例化之前可以使用静态变量。

  class C {
 constructor（x）{
 C. alist = C.alist || []; 
 ... 
} 
 add（x）{...} 
 show（）{...} 
} 
  

I've been hunting around for a clear answer to this, and most of what pops up still relates to the old (or should I say "traditional") way of defining classes using function.

According to this SO answer,

Class properties are not supported in ES2015.

As far as I can tell, the only way to add a static variable to a class is like:

https://jsfiddle.net/abalter/fknwx3n4/

class C {

  constructor(x) {
    console.log("in constructor " + x);
    this.x = x;
    this.add(this.x);
  }

  add(x) {
    console.log("in add " + x);
    C.alist.push(x);
  }

  show() {
    console.log("in show");
    console.log(C.alist);
  }
}

// MUST be done outside of actual class definition.
C.alist = [];

c1 = new C(5);
c1.show();
c2 = new C(10);
c1.show();
c2.show();

Is this the end of the story? Just seems so strange to not be able to do it INSIDE the class definition.

解决方案

You could call a static function that initializes all the static members immediately after the class is defined, and then optionally delete that function. _{(Possibly resetting static variables would be a feature?)}

This would allow you to keep all of your static variables inside the class declaration.

class C {
  static init() {
    C.alist = [];
  }

  constructor(x) {…}
  add(x) {…}
  show() {…}
}
C.init();
delete C.init;

Another option is to initialize static variables in the constructor, but this requires that at least one object be instantiated before the static variables can be used.

class C {
  constructor(x) {
    C.alist = C.alist || [];
    …
  }
  add(x) {…}
  show() {…}
}

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