iframe-example.js

if (!GLOBALS.poll_time) {
    var poll_timeout_seconds = 3;
} else {
    var poll_timeout_seconds = GLOBALS.poll_time;
}

var element = "iframe.locator";
var element_text = "Text to check";

var poll_frequency_ms = 500;
var counter = 0;
var max_loops = Math.round(poll_timeout_seconds * 1000 / poll_frequency_ms);

var checkIframeTextPresent = function (locator, text) {
    if ($(locator).length == 0) return false;
    return $(locator)[0].contentWindow.document.body.textContent.indexOf(text) !== -1;
};

var fn = function waitLoop() {
  if (checkIframeTextPresent(element, element_text)) {
    callback(true);
  } else {
    if (counter == max_loops) {
       return callback("Couldn't find text '"+element_text+"' inside "+element+" in "+poll_timeout_seconds+"s");
       //return callback(true);
    }
    counter++;
    setTimeout(waitLoop, 1000);
  }
}
fn();