H5表单验证不得为空，自定义提示语

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

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