CODEWITHSUNDEEP
javascriptformsvalidation
Shaikat Chakraborty
Shaikat Chakraborty

Reputation: 29

Accept only multiples of 20 (Ex. 40,60,80) on an input field using javascript?

I am a newbie to javascript. I need serious help with a form validation using javascript. Here is what i need the script to perform.

When a user fills a form and he enters numbers other than multiples of 20,(Like 40,60,80,100) he should get an alert.

Example: If i enter 45 on an input field, i should get an error like "You have entered an invalid amount."

{else}

Post form.

Upvotes: 1

Views: 1249

Answers (3)

Robin Winslow
Robin Winslow

Reputation: 11504

@Kooilnc is correct, but here's a more complete solution: http://jsfiddle.net/nottrobin/vN3xK/

<form name="numberForm">
    <input type="number" name="number" />
    <button type="submit">submit</button>
</form>
<script>
    // NB: jQuery is required
    jQuery('[name="numberForm"]').bind(
        'submit',
        function(evt) {
            if(jQuery('[name="number"]').val() % 20 != 0) {
                alert('Your number is wrong');
                evt.preventDefault();
            }
        }
    );
</script>

Can I suggest you use % instead of regex, 'cos it's way much neater.

Upvotes: 0

Kathiravan
Kathiravan

Reputation: 699

In jQuery

if($('#input_id').val() % 20 != 0)
{
    $('#input_id').val('');
    alert('You have entered an invalid amount.');
} 
else 
{ 
    //success
}

Upvotes: 0

KooiInc
KooiInc

Reputation: 122888

Try using the % (modulus) operator

if ((+([value of inputfield])||1)%20 === 0) { /* is multiple of 20 */ }
//   ^convert to Number      ^
//                           ^if conversion fails, use 1 for value
//                            (so %-operation will not fail)

See this jsfiddle for a simple example

Upvotes: 2

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