HTMLMediaElement: progress イベント

addEventListener("progress", (event) => {}); onprogress = (event) => {}; 

<div class="example"> <button type="button">Load video</button> <video controls width="250"></video> <div class="event-log"> <label for="eventLog">Event log:</label> <textarea readonly class="event-log-contents" id="eventLog"></textarea> </div> </div> 

.event-log-contents { width: 18rem; height: 5rem; border: 1px solid black; margin: 0.2rem; padding: 0.2rem; } .example { display: grid; grid-template-areas: "button log" "video log"; } button { grid-area: button; width: 10rem; margin: 0.5rem 0; } video { grid-area: video; } .event-log { grid-area: log; } .event-log > label { display: block; } 

const loadVideo = document.querySelector("button"); const video = document.querySelector("video"); const eventLog = document.querySelector(".event-log-contents"); let source = null; function handleEvent(event) { eventLog.textContent += `${event.type}\n`; } video.addEventListener("loadstart", handleEvent); video.addEventListener("progress", handleEvent); video.addEventListener("canplay", handleEvent); video.addEventListener("canplaythrough", handleEvent); loadVideo.addEventListener("click", () => { if (source) { document.location.reload(); } else { loadVideo.textContent = "Reset example"; source = document.createElement("source"); source.setAttribute( "src", "https://mdn.github.io/learning-area/html/multimedia-and-embedding/video-and-audio-content/rabbit320.mp4", ); source.setAttribute("type", "video/mp4"); video.appendChild(source); } });