var menu = document.getElementById('menu');
var links = menu.getElementsByTagName('a');
for (var i = 0; i < links.length; i++) {
links[i].onclick = function () {
for (var j = 0; j < links.length; j++) {
if(links[j] == this) {
this.style.color = 'red';
} else {
links[j].style.color = '';
}
}
}
}
$(document).ready(function(){
var lea = $(".leftlist ul li a") //申明
lea.click(function(){ //给一个鼠标点击事件
$(this).siblings().show().parent().siblings().children("ul").hide();//同辈元素显示出来，然后父级元素的，同辈元素，子元素ul隐藏
});
})
<script language=javascript type=text/javascript>
function check(obj){
document.getElementById(obj).style.color="#ff0000";
}
</script>
<input id="userid" type="text" name="userid" value="A000000000" onchange="check(this.id)" style="color: black;">