HTML Audio/Video DOM ratechange Event

//Accessing the element
var vid = document.getElementById("myVideo");

//Setting the current playback speed of the video to 0.5
function setPlaySpeed() { 
  vid.playbackRate = 0.5;
} 

//Assign an onratechange event to the video element, and execute a function if the playing speed of the video is changed
vid.onratechange = function() {myFunction()};

//Creating a function
function myFunction() {
  alert("The playing speed of the video was changed");
}

<element onratechange="myScript">

object.onratechange=function(){myScript};

object.addEventListener("ratechange", myScript);