The issue was with the Tiny MCE I was using. So instead of trying to get the value of texte area by
var originalStriped = $("#wysiwyg").val().replace(/(<([^>]+)>)/ig,"");
I had to use the tinyMCE method to fetch the text
var originalStriped = tinyMCE.get("wysiwyg").getContent({format : "text"});
Another problem with TinyMCE is that it doesnot update the data in textarea on an AJAX call, which otherwise, it does on form submit. So I had to call the trigger the save on tinyMCE manually by calling
tinyMCE.triggerSave();
And then firing the AJAX request with form data.