Checking for blank input with jQuery

Question

I'm submitting some comments via $.ajax. However I want to check to make sure that some content is entered in the input box. At the moment I am using this:

if ($("#comments").val().length != 0){

However this only works if a user leaves in the input blank, if the leave a space or return then it will pass. How can I improve this if?

Answer 1

you might go for a trim-function ... google give us some nice links. btw ... jQuery does have a trim-function

eg.

var trimmedValue = jQuery.trim($('#comments').val());
if (trimmedValue.length > 0) {
   // TODO
}

Answer 2

Remove whitespace before checking for empty:

if ($("#comments").val().replace(/^\s+|\s+$/g, "").length != 0){

Answer 3

In JavaScript

//Following all return true
"" == false
" " == false
"  " == false
"   " == false
//Not related to question but interesting
//Following all (also) return true
!" " == false
!"  " == false
!"   " == false
//Except
!"" == false //returns false

(Verified with Firebug console and Chromium's Developer Tools console).