HTM5 checkValidity()方法

HTML5也checkValidity()可以在Google Chrome和Opera中使用。这也可以：
<!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>
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