JSFiddle - React, Tailwind, and code Playground

HTML

<p id='demo'>
</p>

JavaScript

var string = "Hi welcome to stack overflow"
var toSearch = "stack"

//case insensitive search
var result = string.search(new RegExp(toSearch, "i")) > 0 ? 'Matched' : 'notMatched'

document.getElementById("demo").innerHTML = result