JSFiddle - React, Tailwind, and code Playground

HTML

<p id="array">

</p>

JavaScript

var a = ['sara', 'mike', 'sara','sara','Jon'];

for(var i=0; i<a.length; i++){
  	var repeated = 1;
	for(var j=i; j<a.length; j++){
    if(i == j){
    continue;
    }
  	if(a[i].toLowerCase() == a[j].toLowerCase()){
    	a[j] = a[i]+repeated;
      repeated++;
    }
  }
}

document.getElementById("array").innerHTML = a.toString();