JSFiddle - React, Tailwind, and code Playground

by grammar

HTML

<div id="output">Can't find tmgAds...</div>

JavaScript

var output = document.getElementById('output'),
    intervalCounter = 0,
    maxCount = 50,
    i = setInterval(function() {
        if(intervalCounter <= maxCount) {
            console.log("inside interval");
            if(doesTmgAdsExist()) {
                console.log("found it... exiting interval");
                clearInterval(i);
                insertPreviews();
            }
            intervalCounter++;
        } else {
            clearInterval(i);
            output.innerHTML = "Could not find tmgAds after " + maxCount + " attempts... Giving up hope.";
        }
                
    }, 100);
    
function doesTmgAdsExist() {
    return typeof tmgAds !== "undefined";
}

function insertPreviews() {
    console.log("insert previews here...");
    document.getElementById('output').innerHTML = "Found tmgAds!";
}

// Change this variable's value to 10000 to see that the polling will stop
// after `maxCount` attempts
var timeoutAmount = 1000;

setTimeout(function() {
    window.tmgAds = {};
}, timeoutAmount);