The given code will not allowed the user to enter any special characters.Check it.

<script>
function ch(){
var str=document.getElementById("text").value;
var desired = str.replace(/[^\w\s]/gi, '');
document.getElementById("text").value=desired;
}
</script>
<pre>
Enter String <input type="text" id="text" onkeydown="ch();">
</pre>

Then there is a restriction on the characters the user can enter.But how is it that sites like facebook,google and other sites allow the user??In these sites the user can easily enter whatever character he likes??Is there any other solution??