JSFiddle - React, Tailwind, and code Playground

HTML

<div id="the-div"></div>

JavaScript

var targetEl = document.getElementById('the-div');
targetEl.onmouseenter = function() {
  alert('mouseenter triggered');
}

var event;
if (typeof MouseEvent == 'function') {
  // current standard
  event = new MouseEvent('mouseenter', { 'view': window, 'bubbles': true, 'cancelable': true });
  targetEl.dispatchEvent(event);

} else if (typeof document.createEvent == 'function') {
  // older standard
  event = document.createEvent('MouseEvents');
  event.initEvent('mouseenter', true /*bubbles*/, true /*cancelable*/);
  targetEl.dispatchEvent(event);

} else if (typeof document.createEventObject == 'function') {
  // IE 8- 
  event = document.createEventObject();
  targetEl.fireEvent('onmouseenter', event);
}