W3School TIY Editor
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<!DOCTYPE html> <html> <body> <form action="/demo/htmldom/action_page.php"> 复选框：<input type="checkbox" id="myCheck" name="test" required> <input type="submit"> </form> <p>单击“试一试”按钮可查看是否必须在提交表单之前选中该复选框。</p> <button onclick="myFunction()">试一试</button> <p id="demo"></p> <script> function myFunction() { var x = document.getElementById("myCheck").required; document.getElementById("demo").innerHTML = x; } </script> </body> </html>