JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" value="draw" onclick="init();" /><br />
<div id="console-log0"></div>
<script>
function evklid(a,b){
	while(a!=0 || b!=0){
		if(a>b){
			a=a%b;
		}else{
			b=b%a;
		}
	}
	return a+b;
}

function init(){
	var hello=document.getElementById('console-log0');
	
	var ev=evklid(21,14);
	hello.innerHTML=ev;
}
</script>