waitElement in DOM

waitElement.js

function waitElement(selector, callback, delay) {
  delay = delay || 100;
  
  setTimeout(function() {
    if(jQuery(selector).length) {
      callback();
    } else {
      waitElement(selector, callback, delay);
    }
  }, delay);
 
}

waitElement('.test', function() {
  alert(1);
});

setTimeout(function() {
  jQuery(document.body).append('<div class="test">12121<div>');
}, 5000)