Check if inputs are empty using jQuery

Question

I have a form that I would like all fields to be filled in. If a field is clicked into and then not filled out, I would like to display a red background.

Here is my code:

$('#apply-form input').blur(function () {
  if ($('input:text').is(":empty")) {
    $(this).parents('p').addClass('warning');
  }
});

It applies the warning class regardless of the field being filled in or not.

What am I doing wrong?

Answer 1

Doing it on blur is too limited. It assumes there was focus on the form field, so I prefer to do it on submit, and map through the input. After years of dealing with fancy blur, focus, etc. tricks, keeping things simpler will yield more usability where it counts.

$('#signupform').submit(function() {
    var errors = 0;
    $("#signupform :input").map(function(){
         if( !$(this).val() ) {
              $(this).parents('td').addClass('warning');
              errors++;
        } else if ($(this).val()) {
              $(this).parents('td').removeClass('warning');
        }   
    });
    if(errors > 0){
        $('#errorwarn').text("All fields are required");
        return false;
    }
    // do the ajax..    
});

Answer 2

$('#apply-form input').blur(function()
{
    if( !$(this).val() ) {
          $(this).parents('p').addClass('warning');
    }
});

And you don't necessarily need .length or see if it's >0 since an empty string evaluates to false anyway but if you'd like to for readability purposes:

$('#apply-form input').blur(function()
{
    if( $(this).val().length === 0 ) {
        $(this).parents('p').addClass('warning');
    }
});

If you're sure it will always operate on a textfield element then you can just use this.value.

$('#apply-form input').blur(function()
{
      if( !this.value ) {
            $(this).parents('p').addClass('warning');
      }
});

Also you should take note that $('input:text') grabs multiple elements, specify a context or use the this keyword if you just want a reference to a lone element (provided there's one textfield in the context's descendants/children).

Answer 3

Everybody has the right idea, but I like to be a little more explicit and trim the values.

$('#apply-form input').blur(function() {
     if(!$.trim(this.value).length) { // zero-length string AFTER a trim
            $(this).parents('p').addClass('warning');
     }
});

if you dont use .length , then an entry of '0' can get flagged as bad, and an entry of 5 spaces could get marked as ok without the $.trim . Best of Luck.

Answer 4

if ($('input:text').val().length == 0) {
      $(this).parents('p').addClass('warning');
}

Answer 5

Consider using the jQuery validation plugin instead. It may be slightly overkill for simple required fields, but it mature enough that it handles edge cases you haven't even thought of yet (nor would any of us until we ran into them).

You can tag the required fields with a class of "required", run a $('form').validate() in $(document).ready() and that's all it takes.

It's even hosted on the Microsoft CDN too, for speedy delivery: http://www.asp.net/ajaxlibrary/CDN.ashx

Answer 6

The :empty pseudo-selector is used to see if an element contains no childs, you should check the value :

$('#apply-form input').blur(function() {
     if(!this.value) { // zero-length string
            $(this).parents('p').addClass('warning');
     }
});