另一种关于类的小例

前言

我们还是以一段关于构造函数的代码作为开端，我们以之前银行家的小项目为背景

javascript 复制代码

class Account {
  constructor(owner, currency, pin) {
    this.owner = owner;
    this.currency = currency;
    this.pin = pin;
  }
}

const ITshare = new Account('ITshare', 'EUR', '21211');
console.log(ITshare);

● 我们可以设置一个欢迎语

javascript 复制代码

class Account {
  constructor(owner, currency, pin) {
    this.owner = owner;
    this.currency = currency;
    this.pin = pin;
    this.locale = navigator.language;

    console.log(`欢迎来到你的账户，${owner}`);
  }
}

const ITshare = new Account('ITshare', 'EUR', '21211');
console.log(ITshare);

● 但是如果现在我们需要一个存钱和取钱的数组，用于记录，该怎么去做呢？当然我们可以用传统的方法

javascript 复制代码

class Account {
  constructor(owner, currency, pin) {
    this.owner = owner;
    this.currency = currency;
    this.pin = pin;
    this.movements = [];
    this.locale = navigator.language;

    console.log(`欢迎来到你的账户，${owner}`);
  }
}

const ITshare = new Account('ITshare', 'EUR', '21211');
ITshare.movements.push(250);
ITshare.movements.push(-156);
console.log(ITshare);

● 上面未必显得有点不高级了，可以像下面这样的写

javascript 复制代码

class Account {
  constructor(owner, currency, pin) {
    this.owner = owner;
    this.currency = currency;
    this.pin = pin;
    this.movements = [];
    this.locale = navigator.language;

    console.log(`欢迎来到你的账户，${owner}`);
  }

  deposit(val) {
    this.movements.push(val);
  }

  withraw(val) {
    this.deposit(-val);
  }
}

const ITshare = new Account('ITshare', 'EUR', '21211');
ITshare.deposit(250);
ITshare.withraw(120);
console.log(ITshare);

上面的取钱和存钱的操作就属于公共接口，所有人在存钱或者取钱的时候都是调用同样的方法；

● 我们可以像之前那样实现一个贷款的样例

javascript 复制代码

class Account {
  constructor(owner, currency, pin) {
    this.owner = owner;
    this.currency = currency;
    this.pin = pin;
    this.movements = [];
    this.locale = navigator.language;

    console.log(`欢迎来到你的账户，${owner}`);
  }

  deposit(val) {
    this.movements.push(val);
  }

  withraw(val) {
    this.deposit(-val);
  }

  approveLoan(val) {
    return true;
  }

  requestLoan(val) {
    if (this.approveLoan(val)) {
      this.deposit(val);
      console.log('恭喜你！贷款成功');
    }
  }
}

const ITshare = new Account('ITshare', 'EUR', '21211');
ITshare.deposit(250);
ITshare.withraw(120);
ITshare.requestLoan(1000);
console.log(ITshare);

上面的方法中，approveLoan方法只有被requestLoan他才有效，所以在开发中，数据封装和数据隐私非常非常重要，后面的话我们的文章再分享学习