Document: DOMContentLoaded ã¤ãã³ã

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DOMContentLoaded ã¤ãã³ãã¯ãHTML ã®ææ¸ãå®å¨ã«èªã¿è¾¼ã¾ãæ§æè§£æããããã¹ã¦ã®éå»¶ã¹ã¯ãªããï¼<script defer src="â¦"> ããã³ <script type="module">ï¼ããã¦ã³ãã¼ããããå®è¡ãããã¨ãã«çºçãã¾ããç»åããµããã¬ã¼ã ãéåæã¹ã¯ãªããã®èªã¿è¾¼ã¿ã®å®äºã¯å¾ã¡ã¾ããã

å¥ãªã¤ãã³ãã§ãã load ã¯ããã¼ã¸å¨ä½ãèªã¿è¾¼ã¾ããã¨ãã«ã®ã¿ä½¿ç¨ãã¾ãã load ã DOMContentLoaded ãããé©åã§ããå ´é¢ã§ä½¿ã£ã¦ãã¾ããã¨ãããããèª¤ãã§ãã

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ãã®ã¤ãã³ãåã addEventListener() ãªã©ã®ã¡ã½ããã§ä½¿ç¨ããããã¤ãã³ããã³ãã©ã¼ã®ããããã£ãè¨å®ããããã¦ãã ããã

addEventListener("DOMContentLoaded", (event) => {});

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document.addEventListener("DOMContentLoaded", (event) => {
  console.log("DOM fully loaded and parsed");
});

DOMContentLoaded ã®éå»¶

html

<script>
  document.addEventListener("DOMContentLoaded", (event) => {
    console.log("DOM ã¯å®å¨ã«èªã¿è¾¼ã¾ãè§£éããã¾ãã");
  });

  for (let i = 0; i < 1_000_000_000; i++);
  // ãã®åæã¹ã¯ãªããã¯ DOM ã®æ§æè§£æãéãããã®ã§ã
  // DOMContentLoaded ã¤ãã³ãã¯ãã®å¾ã§èµ·åãããã¨ã«ãªãã¾ãã
</script>

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DOMContentLoaded ã¯ã¹ã¯ãªããå®è¡ã®æ©ä¼ãããåã«çºçãããã¨ãããããããªã¹ãã¼ãè¿½å ããåã«ãã§ãã¯ããã®ãè³¢æã§ãã

function doSomething() {
  console.info("DOM loaded");
}

if (document.readyState === "loading") {
  // Loading hasn't finished yet
  document.addEventListener("DOMContentLoaded", doSomething);
} else {
  // `DOMContentLoaded` has already fired
  doSomething();
}

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HTML

html

<div class="controls">
  <button id="reload" type="button">åèªã¿è¾¼ã¿</button>
</div>

<div class="event-log">
  <label for="eventLog">ã¤ãã³ããã°:</label>
  <textarea
    readonly
    class="event-log-contents"
    rows="8"
    cols="30"
    id="eventLog"></textarea>
</div>

body {
  display: grid;
  grid-template-areas: "control log";
}

.controls {
  grid-area: control;
  display: flex;
  align-items: center;
  justify-content: center;
}

.event-log {
  grid-area: log;
}

.event-log-contents {
  resize: none;
}

label,
button {
  display: block;
}

#reload {
  height: 2rem;
}

JavaScript

const log = document.querySelector(".event-log-contents");
const reload = document.querySelector("#reload");

reload.addEventListener("click", () => {
  log.textContent = "";
  setTimeout(() => {
    window.location.reload(true);
  }, 200);
});

window.addEventListener("load", (event) => {
  log.textContent += "load\n";
});

document.addEventListener("readystatechange", (event) => {
  log.textContent += `readystate: ${document.readyState}\n`;
});

document.addEventListener("DOMContentLoaded", (event) => {
  log.textContent += "DOMContentLoaded\n";
});