[ASK] How validate textarea if any code in values?

[ASK] How validate textarea if any code in values?

How validate textarea if any codes like php, jquery, html ..etc 
I usually use this , for validate if textarea empty?


var txtcontent  = jQuery.trim($("form textarea[name='txtcontent']").val()); // email field

if(txtcontent == "") {
$("span.txtcontent_val").html("fields empty.");
val_holder = 1;
} 



so why if any code in textarea and i want replace with <blockquote>..code...</blockquote>

Thanks