bbh-pc/script/video.js

let loopVideo = document.getElementById('loop');
let sourceLoop = document.createElement('source');
sourceLoop.setAttribute('src','./video/loop.mp4');
sourceLoop.setAttribute('type','video/mp4');


window.onload = function(){
    setTimeout(()=>{
        console.log('once');

        loopVideo.appendChild(sourceLoop);
    },12000)
}