JSFiddle - React, Tailwind, and code Playground

JavaScript

var str = '**live its live**   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  <html xmlns="http://www.w3.org/1999/xhtml"> <head><title>  Untitled Page </title><link href="App_Themes/Modern/default.css" type="text/css" rel="stylesheet" /></head> <body>     <form name="form1" method="post" action="/Web/MessageDisplay.aspx" id="form1"> <div> <input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUJNzgzNDMwNTMzZGTa4056JeZHQioLQvNmbYjBQvHt8A==" /> </div>      <div>          </div>     </form> </body> </html>';


alert(str.slice(0,str.indexOf('<!DOCTYPE')))