H5表单验证不得为空，自定义提示语

html代码

<form action="" method="get">
<input type="text" oninput="validateFeeling(this)" required />
<input type="submit"  value="ok" />
</form>

js代码

<script>
 function validateFeeling(input) {
   if (input.value == " ") {
     input.setCustomValidity('此项为必填');
     return false;
   } 
 }
</script>