JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="filterBox"/>
<button type="button" id="filterButton">FILTER</button>

JavaScript

$("#filterButton").click(function()
{
    var filterSubstring = $("#filterBox").val();
    alert("value is now: " + filterSubstring);
    
    var regexp = new RegExp(filterSubstring,"gi");
    
    var filterarray = ["ontwerpbesluitenbundel.dmt", "ontwerpbesluitenbundel_body.xta", "ScriptTemplate.docx", "ShippingOrder.xta", "header.xta"];
    
    for(var i = 0; i < filterarray.length; i++)
    {
        var textToSearch = filterarray[i];
    
        if(!regexp.test(textToSearch))
        {
            alert("NOT OK: " + textToSearch + " DID NOT CONTAIN: " + filterSubstring);  
        }
        else
        {
            alert("OK! " + textToSearch + " CONTAINS: " + filterSubstring);
        }
    }
});