Question

当它进入第21行时，它认为没有功能存款我觉得它应该有这个功能。请解释原因。

1   function makeBankAccount(){
2     var bala = 0
3     function balance(b)
4     {
5       return bala;
6     }
7     function withdraw(b)
8     {
9       bala = bala - b;
10    }
11    function deposit(b)
12    {
13      bala = bala + b;
14    }
15    return makeBankAccount;
16  }
17  
18  var account1 = makeBankAccount();
19  var account2 = makeBankAccount();
20  
21  account1.deposit(5); 
22  console.log(account1.balance()); // -> 5
23  account1.withdraw(5);
24  console.log(account1.balance()); // -> 0
25  
26  account2.withdraw(5);
27  account2.withdraw(5);
28  account2.deposit(5); 
29  account2.deposit(5); 
30  account2.deposit(5);
31  account2.deposit(5);
32  console.log(account2.balance()); // -> 10

Answer 1

这是因为您的函数deposit(b)不是全局函数。

deposit(b)只能在make makeBankAccount()内访问，并且您的对象位于外部。所以deposit(b)超出了范围。

对象创建中也缺少new个关键字。将其更改为：

对象1：

var account1 = new makeBankAccount();

对象2：

var account2 = new makeBankAccount();

Answer 2

有两种方法可以做到这一点：

function makeBankAccount(){
    var bala = 0

    function balance(b) {
        return bala;
    }

    function withdraw(b) {
        bala = bala - b;
    }

    function deposit(b) {
        bala = bala + b;
    }
    return {
        balance: balance,
        withdraw: withdraw,
        deposit: deposit
    };
}

然后您的使用代码将保持不变

或

function makeBankAccount(){
    this.bala = 0
}

makeBankAccount.prototype.balance = function(b) {
    return this.bala;
};

makeBankAccount.prototype.withdraw = function(b) {
    this.bala -= b;
};

makeBankAccount.prototype.deposit = function (b) {
    this.bala += b;
};

然后你的实例化帐户1 /帐户2就像

var account1 = new makeBankAccount();
var account2 = new makeBankAccount();

其余代码保持不变

Answer 3

试试这个：

var balance = 10; //You may have the balance saved anywhere else. Get it here.
var makeBankAccount = {
    amount: 0,
    balance: function () {
        return balance;
    },
    withdraw: function () {
        return balance - this.amount;
    },
    deposit: function () {
        return balance + this.amount;
    }
}
function Balance() {
  document.getElementById("Balance").innerHTML = makeBankAccount.balance();
}
function Withdraw(x) {
  makeBankAccount.amount = x;
  document.getElementById("Withdraw").innerHTML = makeBankAccount.withdraw();
}
function Deposit(x) {
  makeBankAccount.amount = x;
  document.getElementById("Deposit").innerHTML = makeBankAccount.deposit();
}

<html>
<body>
  <button onclick="Balance()">Balance</button>
  <button onclick="Withdraw(6)">Withdraw</button>
  <button onclick="Deposit(7)">Deposit</button>
  <p id="Balance"></p>
  <p id="Withdraw"></p>
  <p id="Deposit"></p>
</body>
</html>

剩下的就是获取balance并将amount传递给函数。

JAvascript＆＃34;没有方法＆＃34;

3 个答案: