Removing everything except numbers in a string

Question

I've made a small calculator in javascript where users enter the interest rate and amount the they want to borrow, and it calculates how much of an incentive they might get.

The problem is that I'm worried users will enter symbols, e.g.

Loan amount: £360,000 - Interest Rate: 4.6%

I'm not worried about the decimal places as these are needed and don't seem to affect the calculation, it's the symbols like £ and % which mess things up.

Is there a simple way to strip out these symbols from the code:

<td><input type="text" name="loan_amt" style="background-color:#FFF380;"></td>
<td><input type="text" name="interest_rate" style="background-color:#FFF380;"></td>


function Calculate()
{
    var loan_amt = document.getElementById('loan_amt').value;
    //this is how i get the loan amount entered
    var interest_rate = document.getElementById('interest_rate').value; 
    //this is how i get the interest rate

    alert (interest_rate);
}

Answer 1

Note that you should use the correct DOM id to refer via getElementById. You can use the .replace() method for that:

var loan_amt = document.getElementById('loan_amt');
loan_amt.value = loan_amt.value.replace(/[^0-9]/g, '');

But that will remove float point delimiter too. This is an answer to your question, but not a solution for your problem. To parse the user input as a number, you can use parseFloat() - I think that it will be more appropriate.

Answer 2

This is the shortest:

replace(/\D/g,'');