对象与数据结构

使用Getter和Setter方法

通过Getter和Setter方法访问对象数据相比直接访问属性更具优势。你可能会问："为什么？" 以下是一个未详细分类的理由列表：

• 当需要在获取对象属性之外进行更多操作时，无需查找并修改代码中的每个访问点
• 执行set操作时可轻松实现数据验证
• 封装内部表示形式
• 便于在属性存取时添加日志记录与错误处理
• 支持属性延迟加载，例如从服务器按需加载数据

反例:

function makeBankAccount() {
  // ...

  return {
    balance: 0
    // ...
  };
}

const account = makeBankAccount();
account.balance = 100;

正例:

function makeBankAccount() {
  // this one is private
  let balance = 0;

  // a "getter", made public via the returned object below
  function getBalance() {
    return balance;
  }

  // a "setter", made public via the returned object below
  function setBalance(amount) {
    // ... validate before updating the balance
    balance = amount;
  }

  return {
    // ...
    getBalance,
    setBalance
  };
}

const account = makeBankAccount();
account.setBalance(100);

使对象具有私有成员

可通过闭包机制实现（适用于ES5及以下版本）

反例:

const Employee = function(name) {
  this.name = name;
};

Employee.prototype.getName = function getName() {
  return this.name;
};

const employee = new Employee("John Doe");
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
delete employee.name;
console.log(`Employee name: ${employee.getName()}`); // Employee name: undefined

正例:

function makeEmployee(name) {
  return {
    getName() {
      return name;
    }
  };
}

const employee = makeEmployee("John Doe");
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
delete employee.name;
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe