CODEWITHSUNDEEP
javascriptjquery
Sam Tyson
Sam Tyson

Reputation: 4616

Negative values not allowed

What is the best way to prevent users from entering negative values in an input text element?

Currently I am checking the field value on blur, but I am hoping somebody has a better solution.

$(".payment").blur(function() {
    var payment = getAmount($(this).val());
    if(!isNaN(payment) && amount >= 0) {
        $(this)
            .css("color", "black")
            .val(currency(payment));
    } else {
        if(amount < 0) showMessage("Negative amounts are not allowed", "error");
        $(this).css("color", "red");
    }
});

function getAmount(strAmount) {
    var amount = new String(strAmount).replace(/\$/g, "").replace(/,/g, "");
    return parseFloat(amount);
}

Upvotes: 2

Views: 16929

Answers (5)

David Thomas
David Thomas

Reputation: 253308

On the assumption you might not want to work with key-codes (e.which, e.keyCode and so on), here's one further option:

$('#a').blur(
    function(){
        var v = $(this).val(),
            t = parseInt(v,10),
            b = isNaN(t);
        if (b){
            $(this).val('');
        }
        else {
            $(this).val(Math.abs(t));
        }
    });​

JS Fiddle demo.

References:

Upvotes: 2

Sam Tyson
Sam Tyson

Reputation: 4616

Thanks for all of the answers.

Here is what I ended up with:

$("input.payment").keypress(function(e) {
    validateNumeric(e);
});

function validateNumeric(evt) {
   var theEvent = evt || window.event;
   var key = theEvent.keyCode || theEvent.which;
   key = String.fromCharCode( key );
   var regex = /[0-9]|\./;
   if( !regex.test(key) ) {
      theEvent.returnValue = false;
      if(theEvent.preventDefault) theEvent.preventDefault();
   }
}

Upvotes: 0

sachleen
sachleen

Reputation: 31131

You can use jQuery's keypress or keydown events to test against the input on every key.

If you haveother fields that need validating as well, consider jQuery Validation plugin.

Upvotes: 1

Andrew Odri
Andrew Odri

Reputation: 9422

This ought to do the trick:

$(".payment").keydown(function(event) {
    if (event.keyCode == 45 ) { event.preventDefault(); }   
});

This will prevent the keydown event from registering when the character code for "-" (45) is detected.

Upvotes: 2

ayyp
ayyp

Reputation: 6598

You could use jQuery's .keypress() and prevent the default action for the - key. Example: http://jsfiddle.net/5cgXg/


$("#target").keypress(function(event) {
  if ( event.which == 45 || event.which == 189 ) {
      event.preventDefault();
   }
});

Upvotes: 9

Related Questions