Periodically check for a given text on a site

Checker.user.js

// ==UserScript==
// @name     Checker
// @version  1
// @description  Check all text on a site for a keyword.
// @author       Peter Zhang
// @match        !!!!!Put what site you want to check on!!!!!
// @grant    none
// ==/UserScript==

const SEARCH_TEXT = "PUT TEXT HERE";

// create a function called reload that reloads the page
function reload() {
if (document.getElementsByClassName("changeme") == SEARCH_TEXT) { // change this to whatever class will have your text
        window.alert("You found the text!")
        window.focus()
    }
    else{
    location.reload();
    }
}


function setup() {
    // check after 30 seconds
    setTimeout(reload, 30000);
}

window.addEventListener("load", setup, false);