Question

here is the code sample:
HTML:

 <form id="information" name="information" action="#" method="post"> 
 <textarea name="text" rows="10" cols="10"> 
 </textarea> 
 <input type="submit" value="submit"/> 
 </form> 

Javascript:

 window.onload=init;

 function init(){
 document.getElementById('information').onsubmit=validateForm;
 }

 function validateForm(){ 
 var text= document.information.text.value; 
 if(text==""){ 
 alert('text area cannot be empty');
 return false;
 } 
 }

it does not work…

Answer 1

The textarea has a carriage return in it (and a space), so your condition is never true. So change it to:

<textarea name="text" rows="10" cols="10"></textarea> 

However you may want to go further and stop the user entering an “empty” response (meaning nothing but white-space). Or you may just want to remove leading and trailing white-space. If so you can do this:

text = text.trim();

Now trim() I believe is relatively new (Firefox lists it as new in 3.5). A more backwards compatible version is:

text = text..replace(/^\s\s*/, '').replace(/\s\s*$/, '');

and then testing if it’s empty.

Faster JavaScript Trim has a good analysis on various white-space trimming alternatives. For instance the above can be done with one regex:

text = text..replace(/^\s+|\s+$/g, '');

but

This commonly thought up approach is
easily the most frequently used in
JavaScript libraries today. It is
generally the fastest implementation
of the bunch only when working with
short strings which don’t include
leading or trailing whitespace. This
minor advantage is due in part to the
initial-character discrimination
optimization it triggers. While this
is a relatively decent performer, it’s
slower than the three methods above
when working with longer strings,
because the top-level alternation
prevents a number of optimizations
which could otherwise kick in.