JSFiddle - React, Tailwind, and code Playground

HTML

<!-- I am passing a string of `country code` into `new RegExp` and wanted to replace with the blank space if there is country code available in mobile number. 
-->
<script>
window.onload = callme();
function callme()
{
	var mobileNum = "2341234567890";
	
	var countryCode = "234";
	
	var re = new RegExp(/^234+/i);
	
	//var re = new RegExp('\\{'+countryCode+'\\}','gi');
	
	//var re = new RegExp("ReGeX" + countryCode + "ReGeX");

	var againNew = mobileNum.replace(re, ''); 
	
	alert(againNew);
}
</script>