HTM5 checkValidity()方法
HTML5也checkValidity()可以在GoogleChrome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>