javascript - ES6 中的内部类占用更多内存？

Question

如果我在构造函数中创建一个内部类，它是否会为我创建的外部类的每个实例分配内存？例如，

class PriorityQueue {
  constructor(maxSize) {
    // Set default max size if not provided
    if (isNaN(maxSize)) {
      maxSize = 10;
    }
    this.maxSize = maxSize;

    // Init an array that'll contain the queue values.
    this.container = [];

    // Create an inner class that we'll use to create new nodes in the queue
    // Each element has some data and a priority
    this.Element = class {
      constructor(data, priority) {
        this.data = data;
        this.priority = priority;
      }
    };
  }
}

是否为 Priority Queue 类的每个实例创建了 Element 类？有没有办法让这个类静态化？

Answer 1

因为您正在构造函数中创建类并将其分配给 this.Element，并且每次实例化 PriorityQueue 时构造函数都会运行 - 是的，您正在创建新的Class 用于每个实例。如果您只想为所有实例化一个类，请将其放在原型(prototype)上:

class PriorityQueue {
  constructor(maxSize) {
    // Set default max size if not provided
    if (isNaN(maxSize)) {
      maxSize = 10;
    }
    this.maxSize = maxSize;

    // Init an array that'll contain the queue values.
    this.container = [];
  }
}
PriorityQueue.prototype.Element = class {
  constructor(data, priority) {
    this.data = data;
    this.priority = priority;
  }
}

const p1 = new PriorityQueue(1);
const p2 = new PriorityQueue(2);
console.log(p1.Element === p2.Element);