Simulate onMouseOver

https://stackoverflow.com/questions/37231201/

HTML

<div id="menu">
  <h3> Menu </h3>
  <div>
  This is a sample to show how to fire / dispatch an onmouseover event using a script. This can be used to automate webtesting. 
  </div>
  <ul>
   <li>one</li>
   <li>two</li>
   <li>three</li>
  </ul>
</div>
<button onclick="simulateMouseOver()">simulate onMouseOver</button>

JavaScript

// https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/dispatchEvent
// 
// https://developer.mozilla.org/en-US/docs/Web/Events/mouseover
// handler executes every time the cursor 
// is moved over an element inside div#menu

  var menu =  document.getElementById("menu");
  menu.addEventListener("mouseover", function( event ) {   
    // highlight the mouseover target
    event.target.style.backgroundColor = "blue";
    // reset the color after a short delay
    setTimeout(function() {
      event.target.style.backgroundColor = "";
    }, 500);
  }, false)();

function simulateMouseOver() {
  var listItems = document.querySelectorAll("ul li")
	var item1 = listItems.item(1);
  var event = new MouseEvent('mouseover', {view: window, bubbles: true, cancelable: true});
  // var cb = document.getElementById('checkbox'); 
  var cancelled = !item1.dispatchEvent(event);
  if (cancelled) {
    // A handler called preventDefault.
    //  alert("cancelled");
  } else {
    // None of the handlers called preventDefault.
    // alert("not cancelled");
  }
}