waitForElement.js

waitForElement.js

function waitForElement(selector) {
  return new Promise(function(resolve, reject) {
    var element = document.querySelector(selector);

    if(element) {
      resolve(element);
      return;
    }

    var observer = new MutationObserver(function(mutations) {
      mutations.forEach(function(mutation) {
        var nodes = Array.from(mutation.addedNodes);
        for(var node of nodes) {
          if(node.matches && node.matches(selector)) {
            observer.disconnect();
            resolve(node);
            return;
          }
        };
      });
    });

    observer.observe(document.documentElement, { childList: true, subtree: true });
  });
}

It is pretty simple to use this simple API.

waitForElement("#test").then(function(element) {
console.log("Element Added", element);
});
Now combining in the monitorEvents function from my previous post, I can now set a breakpoint early in the lifecycle of a page (because scripts in the head block) and set up a waitForElement call that can now start logging all the events that are firing on that element.

waitForElement("#test").then(function(element) {
monitorEvents(element);
});