audio play background running in javascript code example

Example 1: play a sound wiith js

var audio = new Audio('audio.mp3');
  audio.play();

Example 2: play sound in javascript

<script>
function play() {
  var audio = new Audio('https://interactive-examples.mdn.mozilla.net/media/examples/t-rex-roar.mp3');
  audio.play();
}
</script>
<button onclick-"play();">PLAY MY AUDIO</button>