If statement that checks for negative numbers

Question

I have a bank script. When the user deposits money I want to make sure it is a positive integer. If it isn't, I want to kick them out.

Here is my code:

<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;
}

I tried using ..

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

But that doesn't work. What am I doing wrong?

Thanks guys!

`But that doesn't work` What does it mean? do you get an error? — gurvinder372, Apr 12 '17 at 06:47
http://stackoverflow.com/questions/10834796/validate-that-a-string-is-a-positive-integer — Jurij Jazdanov, Apr 12 '17 at 06:48
Possible duplicate of [Validate that a string is a positive integer](http://stackoverflow.com/questions/10834796/validate-that-a-string-is-a-positive-integer) — Koby Douek, Apr 12 '17 at 06:49

score 1 · Accepted Answer · answered Apr 12 '17 at 06:56

Just check

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

Rewrite your if loop as if - else if - else to avoid checking all conditions.

 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-->

score 1 · Answer 2 · answered Apr 12 '17 at 07:12

1

Check like this:

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

answered Apr 12 '17 at 07:12

w.p

341
2
7

If statement that checks for negative numbers

2 Answers2