document.querySelectorAll('video').forEach(
el => el.addEventListener('play', function(event) {
console.log(this)
})
)
https://jsfiddle.net/c0b94wuq/document.addEventListener('play', function(event) {
console.log(event.target)
}, true) /* обязательно! */
https://jsfiddle.net/c0b94wuq/1/