Below code disables 0 as the first character in #foo.
However, you can bypass this by typing 123, then drag to select 123 and putting 0. (or ctrl+a on input)
Is there a way to block this scenario?
$('input#foo').keypress(function(e){ if (this.value.length == 0 && e.which == 48 ){ return false; } });<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <input id="foo" />I would handle the input, propertychange, and paste events. Then use regex to match for anything that begins with 0 and replace the current value with the value minus the leading 0.
http://jsfiddle.net/SeanWessell/5qxwpv6h/
$('input ').on('input propertychange paste', function (e) { var val = $(this).val() var reg = /^0/gi; if (val.match(reg)) { $(this).val(val.replace(reg, '')); } }); Bug fix reported by Kevin/Updated per recommendations of canon:
http://jsfiddle.net/SeanWessell/5qxwpv6h/2/
$('input').on('input propertychange paste', function (e) { var reg = /^0+/gi; if (this.value.match(reg)) { this.value = this.value.replace(reg, ''); } }); 
123000 and then delete 123. You're left with 00. I'd suggest using the regex ^0+.
$(this).val() instead of this.value? It's unnecessary overhead. 2.: If you insist on $(this), why aren't you caching your jQuery objects? 3.: Why are you looping instead of just updating the regex? I'm worried over the fact that this answer has attracted so many upvotes.
RegExp.prototype.test() rather than String.prototype.match(). You're not really doing anything with the string value returned from match() other than banking on its truthy/falsey coerced value. test() simply returns true or false outright.I think you're looking for the keydown jQuery event as opposed to the keypress event. Here's some move info on the difference between the two. Try regex to get rid of leading zeroes:
$('input#foo').keydown(function(e){ this.value = this.value.replace(/^0+/, ''); }); 
Here's the fixed version :
<input id="foo" /> $('input#foo').keyup(function(e){ if(this.value.substring(0,1) == "0") { this.value = this.value.replace(/^0+/g, ''); } }); jsfiddle : http://jsfiddle.net/ewmb1yq9/4/
This could work:
$('input#foo').keyup(function(e) { if((this.value+'').match(/^0/)) { this.value = (this.value+'').replace(/^0+/g, ''); } }); The only thing that could bother you with this solution is that zero is displayed for a second and then deleted, since we are using keyup event.
Accept only numeric values not prefixed by zero. Supports Ctrl + A:
var escapeKeys = [8, 46]; $('input#foo').keyup(function (e) { if ($.inArray(e.keyCode, escapeKeys) != 0) { if ((this.value + String.fromCharCode(e.keyCode)).match(/^[1-9][0-9]*$|^$/) != null) { this.lastValidValue = this.value + String.fromCharCode(e.keyCode); } else if (this.lastValidValue) { this.value = this.lastValidValue; } else { this.value = ""; } } else { this.lastValidValue = this.value; } });<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <input id="foo" />If you want to catch the changes to the input's value (including the changes made by dragging part of the text for example), you can watch the input event.
$('input#foo').on("input", function(){ alert($(this).val()); });<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <input id="foo" />You could add a "submit" event to validate whether it's entered or not, regardless of how it could have gotten there:
$( "form" ).submit(function( event ) { if ( $( "input:first" ).val() != 0 ) { $( "span" ).text( "Validated..." ).show(); return; } $( "span" ).text( "Not valid!" ).show().fadeOut( 1000 ); event.preventDefault(); });<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script> <p>Type 'Anything but 0' to validate.</p> <form action="javascript:alert( 'success!' );"> <div> <input type="text"> <input type="submit"> </div> </form> <span></span> jQuery's working is example is last on page here (https://api.jquery.com/submit/)
NOTE: The most important part will be to add the "event.preventDefault()" action, because that will keep the form from accidentally submitting.
<input pattern="^[^0]\d+">