JS闭包对象共享状态异常：为何无法得到负分结果？

你的代码中，studentHolberton是一个立即执行函数表达式（IIFE），内部的privateScore和name是整个IIFE的闭包变量——所有通过Object.create(studentHolberton)创建的实例，都会共用这两个变量。

实际执行流程：

• Jerry的4次奖励操作将privateScore累加至4
• Dray的操作是在4的基础上计算：+1后变为5，再减3最终得到2，所以输出Dray: 2，而非预期的-2

要让每个学生拥有独立的私有状态，需要把studentHolberton改成工厂函数，每次调用都会创建新的闭包环境，生成独立的私有变量：

function createStudentHolberton() {
  let privateScore = 0;
  let name = null;

  function changeScoreBy(points) {
    privateScore += points;
  }

  return {
    setName: (newName) => {
      name = newName;
    },
    rewardStudent: () => {
      changeScoreBy(1);
    },
    penalizeStudent: () => {
      changeScoreBy(-1);
    },
    getScore: () => {
      return `${name}: ${privateScore}`;
    },
  };
}

// 创建独立实例
const jerry = createStudentHolberton();
jerry.setName('Jerry');
jerry.rewardStudent();
jerry.rewardStudent();
jerry.rewardStudent();
jerry.rewardStudent();

console.log(jerry.getScore()); // Jerry: 4

const dray = createStudentHolberton();
dray.setName('Dray');
dray.rewardStudent();
dray.penalizeStudent();
dray.penalizeStudent();
dray.penalizeStudent();

console.log(dray.getScore()); // Dray: -2

如果使用现代JavaScript，也可以用ES6类结合私有字段（#前缀）实现，语法更清晰：

class StudentHolberton {
  #privateScore = 0;
  #name = null;

  #changeScoreBy(points) {
    this.#privateScore += points;
  }

  setName(newName) {
    this.#name = newName;
  }

  rewardStudent() {
    this.#changeScoreBy(1);
  }

  penalizeStudent() {
    this.#changeScoreBy(-1);
  }

  getScore() {
    return `${this.#name}: ${this.#privateScore}`;
  }
}

const jerry = new StudentHolberton();
jerry.setName('Jerry');
jerry.rewardStudent();
jerry.rewardStudent();
jerry.rewardStudent();
jerry.rewardStudent();

console.log(jerry.getScore()); // Jerry: 4

const dray = new StudentHolberton();
dray.setName('Dray');
dray.rewardStudent();
dray.penalizeStudent();
dray.penalizeStudent();
dray.penalizeStudent();

console.log(dray.getScore()); // Dray: -2

内容的提问来源于stack exchange，提问作者Saheedat