是否有浏览器还支持HTML5的checkValidity()方法？

是的，checkValidity()在Google Chrome和Opera中也可以使用。这也很好-

示例

<!DOCTYPE html>
<html>
   <body>
      <style>
         .valid {
            color: #0B7866;
         }
         .invalid {
            color: #0B6877;
         }
      </style>

      <div id = "result"></div>
      <script>
         function check(input) {
            var out = document.getElementById('result');
            if (input.validity) {
               if (input.validity.valid === true) {
                  out.innerHTML = "<span class='valid'>" + input.id +
                  " valid</span>";
                  } else {
                  out.innerHTML = "<span class='invalid'>" + input.id +
                 " not valid</span>";
               }
            }
            console.log(input.checkValidity());
         };
      </script>

      <form id = "testform" onsubmit = "return false;">
         <label>Minimum:
            <input oninput = "check(this)" id = "min_input"
            type = number min=4 />
         </label><br>
      </form>
   </body>
</html>

基础教程