CODEWITHSUNDEEP
javascriptvalidationzero
mengmeng
mengmeng

Reputation: 1496

Prevent inputting leading 0

I can input

0 but not 0123. How do I prevent users not to input 0 at the first position of the input text field?

Upvotes: 2

Views: 3910

Answers (2)

Rahul Desai
Rahul Desai

Reputation: 15491

One way to do this is to check the first character in the input using charAt().

Demo

JS:

function check(){
    var number = document.getElementById('input').value;
    if(number.charAt(0) === 0)
        alert('Leading zero in the input.')
    else
        alert('No leading zero in the input.')
}

EASIER SOLUTION:

For the input, just check the first character like an array:

if(number[0] === '0')
        // do something

Demo

Upvotes: 0

Mark Reed
Mark Reed

Reputation: 95242

Let them input it, just trim it when focus changes:

inputElement.onblur = function() {
  this.value = this.value.replace(/^0+(?=\d)/,'');
}

Fiddle

Note that it's specifically looking for a digit (\d) after the 0's that it's nuking, so it won't touch the zero in something like 0.123. If you want to get rid of those, too, just change the \d to ., which matches any character whatsoever.

Upvotes: 5

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