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<!DOCTYPE html> <html> <body> <h1>Window 对象</h1> <h2>setTimeout() 和 clearTimeout() 方法</h2> <button onclick="startCount()">开始计时！</button> <input type="text" id="demo"> <button onclick="stopCount()">停止计时！</button> <p>点击“开始计时！”可启动定时器。输入字段将始终计数，从 0 开始。</p> <p>点击“停止计时！”可停止计数。点击“开始计时！”可再次启动定时器。</p> <script> let counter = 0; let timeout; let timer_on = 0; function timedCount() { document.getElementById("demo").value = counter; counter++; timeout = setTimeout(timedCount, 1000); } function startCount() { if (!timer_on) { timer_on = 1; timedCount(); } } function stopCount() { clearTimeout(timeout); timer_on = 0; } </script> </body> </html>