这个代码该如何实现，急

<!DOCTYPE html>
<html>
	<head>
		<title>Test</title>
		<meta charset="utf-8">
	</head>
	<body>
		<form>
			<input placeholder="手机" id="phone" onfocus="focus()" onblur="blur()"/>
		</form>
	</body>
	<script type="text/javascript">
		
		function blur() {
			var phone = document.getElementById("phone");
			if (phone.innerText) {
				phone.style.borderColor = "black";
			}
		}
		function focus() {
			var phone = document.getElementById("phone");
			if (phone.innerText) {
				phone.style.borderColor = "gray";
			}
		}
	</script>

</html>
望采纳