Tried a way to make the webpage play the background music automatically but it doesn’t seem to work?

Currently in the project, I hope to be able to play background music as soon as you enter the webpage, but chrome seems to have banned this!

Find a way to crack on the Internet, the reference website is as follows:
http://www.nooong.com/docs /chrome_video_autoplay.htm

But I tried to use the above method by myself, the effect is still useless.
I would like to ask you to help me to see if the spelling is wrong, or is it useless at all?

Maybe you have had similar needs, I hope you can share with me, I will be very grateful for your warm help, thank you again Everyone watch my question.

 let trigger = document.querySelector('.trigger');
    let autoplay = document.querySelector('.autoplay');
    trigger.onload = function(){
        autoplay.src = 'demo.mp3';
        autoplay.oncanplay = function(){
        autoplay.play();
        };
    };

<!-- background music to play -->
    <audio autoplay="autoplay" controls="controls" loop ="loop" preload ="auto"  class="autoplay">
        <source src="demo.mp3" />
    </audio>

    <!-- First trigger the audio in the iframe, put an empty music file in it -->
    <iframe allow="autoplay" style="display:none"  class="trigger" src="demo.mp3"></iframe>