Question

<input type="text" class="dot"> <br />
<input type="text" class="dot"> <br />
<input type="text" class="dot"> <br />

$('.dot').keydown(function(){
        $(this).val($(this).val().toString().replace(/\./g, ','));
})

http://jsfiddle.net/ZtkBW/

In this example i replace dot to comma. How can i block the addition of two commas in current input?

If in input is already one comma then next should be remove.

Answer 1

This is a classic case of trying to solving a problem with regular expressions, and now you have two problems…

It’s not clear exactly what you want, but this will stop multiple presses of the comma key. It should be a short step from here to detect the period (code 190) and do whatever you want with it instead.

$('.dot').keydown(function(e){
    if (e.which == 188) {
        if (this.value.indexOf(',') != -1) {
            e.preventDefault();
            return false;
        }
    }
})​;