JSFiddle - React, Tailwind, and code Playground

HTML

<div id="#resultdiv"></div>

JavaScript

function firstOrDefault ( arr, f ) 
{
    var result = null;
    for ( var i = 0, n = arr.length; i < n; ++i )
    	if (f(i)) return i;         
    return result;
}

$(document).ready(function(){
    var myArray = [1, 5, 9, 18];
    var myFunction = function ( x ) { return x > 5; };
	$('#resultdiv').text(firstOrDefault(myArray, myFunction)); // should print 9 inside #resultdiv
});