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<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>本教程(w3big.com)</title> </head> <body> <form action="form_action.asp"> 主页: <input type="url" id="myURL" name="website"> <input type="submit" value="提交"> </form> <p>点击 "点我" 按钮设置 URL 字段的 required 属性。</p> <p><strong>提示:</strong> 在点击 “点我” 按钮前后点击 "提交" 按钮查看效果</p> <button onclick="myFunction()">点我</button> <p id="demo"></p> <script> function myFunction() { document.getElementById("myURL").required = true; document.getElementById("demo").innerHTML = "required 属性已设置。表单提交前 URL 字段为必填字段。"; } </script> </body> </html>