<!DOCTYPE html> <html> <body> <h1>Document 对象</h1> <h2>hasFocus() 方法</h2> <p>单击此文档内部可获得焦点。<br> 单击此文档外部可失去焦点。</p> <p id="demo"></p> <script> setInterval("myFunction()", 1); function myFunction() { let text; if (document.hasFocus()) { text = "本文档获得焦点。"; } else { text = "本文档未获得焦点。"; } document.getElementById("demo").innerHTML = text; } </script> </body> </html>