如何在 JavaScript 中檢查文件是否準備就緒？

以下是如何在 JavaScript 中檢查文件是否準備就緒的程式碼 −

示例

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   }
   .result {
      font-size: 18px;
      font-weight: 500;
      color: blueviolet;
   }
</style>
</head>
<body>
<h1>Check if a document is ready</h1>
<div class="result"></div>
<button class="Btn">Check</button>
<h3>Click on the above button to see document state</h3>
<script>
   let resEle = document.querySelector(".result");
   let BtnEle = document.querySelector(".Btn");
   resEle.innerHTML = document.readyState + "<br><br>";
   BtnEle.addEventListener("click", () => {
      if (document.readyState === "complete") {
         resEle.innerHTML = "The page has finished loading completely";
      } else {
         resEle.innerHTML = "The page is still loading";
      }
   });
</script>
</body>
</html>