JSFiddle - React, Tailwind, and code Playground

HTML

<button class="preview">click to preview</button>
<button class="download">CLick to Download</button>

JavaScript

$(document).ready(function(){
		var rohit = "<h2>Hello i m Dynamic Heading </h2>";
    	$('.preview').on('click', function(){
            var myWindow = window.open('', "rohit", "width=800, height=400", '_blank');
			myWindow.document.write(rohit);
        });
    
    
    	$('.download').on('click', function(){
        	alert(rohit);
            //  here download code with html format how to do this .
        });
});