JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container" contenteditable>
    <p class="editor">test</p>
</div>

<!-- KOPIERA BARA DETTA TEST -->
<!-- something function() { run this (); } -->

CSS

purple {
    color: purple;
}

JavaScript

$("#container").on("keyup", function(){
	$(".editor").each(function(){    
        var fStr = "function";
        var fPos = $(this).text().indexOf(fStr);

        if (fPos >= 0) {
            var pre = $(this).text().substr(0, fPos);
            var after = $(this).text().substr(fPos + fStr.length, $(this).text().length);
            $(this).html(pre + "<purple>" + fStr + "</purple>" + after);
        }
  });  
})