I would like to add a colored wiggly underline to certain text fragments of a element. The effect would be similar to that of spell checkers.>
I dont think this is possible within a textarea, most WYSIWYG editors online use a contenteditable div or iframe made to look like a textarea to style the text within the innerHTML of those elements and therefore display on the front end, you can then get the textContent or innerText of the div/iframe. Using jQuery you could do something like:
this is the wrd
$('#editor').html($('#editor').html().replace("wrd", "wrd"));
not tested at all but should style the div correctly. you could then use $('#editor').text() to retrieve the text value.