javascript - 检查负数的 If 语句

Question

我有一个银行脚本。当用户存钱时我想确保它是一个正整数。如果不是的话，我想把他们踢出去。

这是我的代码:

<section id="pigBox">
      <img src="images/pig.png" />
      <label>Balance: </label><input type="text" id="balance" />
      <button id="deposit"> Deposit </button>
      <button id="withdraw"> Withdraw </button>
  </section><!-- end of pigBox-->

document.getElementById('balance').value = "1000"

var balance = document.getElementById('balance').value;
var deposit = document.getElementById('deposit');
var withdraw = document.getElementById('withdraw');

deposit.addEventListener('click', depositCash);
withdraw.addEventListener('click', withdrawCash);

function depositCash() {
  var depositAmt = prompt('How much would you like to deposit?');

  if(depositAmt != Number(depositAmt) && depositAmt) {
    return alert('Please enter a valid integer.');

  }
  balance = Number(balance) + Number(depositAmt);
  document.getElementById('balance').value = balance;
}

function withdrawCash() {
  var withdrawAmt = prompt('How much you you like to withdraw?');

  if(withdrawAmt != Number(withdrawAmt)) {
    return alert('Please enter a valid integer.');

  }
  balance = Number(balance) - Number(withdrawAmt);
  document.getElementById('balance').value = balance;
}

我尝试使用..

else if(Number(depositAmt) < 0) {
 return alert('please enter a valid integer.');
}

但这行不通。我做错了什么？

谢谢大家!

Answer 1

只需检查

if (depositAmt <= 0) {
    return alert('Please enter a positive integer.');
  }

将 if 循环重写为 if - else if - else 以避免检查所有条件。

 if (depositAmt != Number(depositAmt) && depositAmt) {
    return alert('Please enter a valid integer.');

  } else if (depositAmt <= 0) {
    return alert('Please enter a positive integer.');

  } else {
    balance = Number(balance) + Number(depositAmt);
    document.getElementById('balance').value = balance;
  }

document.getElementById('balance').value = "1000"
var balance, deposit, withdraw;
balance = document.getElementById('balance').value;
deposit = document.getElementById('deposit');
withdraw = document.getElementById('withdraw');

deposit.addEventListener('click', depositCash);
withdraw.addEventListener('click', withdrawCash);

function depositCash() {
  var depositAmt;
  depositAmt = prompt('How much would you like to deposit?');

  if (depositAmt != Number(depositAmt) && depositAmt) {
    return alert('Please enter a valid integer.');

  } else if (depositAmt <= 0) {
    return alert('Please enter a positive integer.');

  } else {
    balance = Number(balance) + Number(depositAmt);
    document.getElementById('balance').value = balance;
  }
}

function withdrawCash() {
  var withdrawAmt;
  withdrawAmt = prompt('How much you you like to withdraw?');

  if (withdrawAmt != Number(withdrawAmt)) {
    return alert('Please enter a valid integer.');

  }
  balance = Number(balance) - Number(withdrawAmt);
  document.getElementById('balance').value = balance;
}

<section id="pigBox">
  <img src="images/pig.png" />
  <label>Balance: </label><input type="text" id="balance" />
  <button id="deposit"> Deposit </button>
  <button id="withdraw"> Withdraw </button>
</section>
<!-- end of pigBox-->