js removeChild 障眼法 可能出现的错误

<ul id="demo">
<li>a</li>
<li>b</li>
<li>c</li>
</ul>

var ul = document.getElementById('demo');
var liList = ul.getElementsByTagName('li');
for (var i = 0; i < = liList.length; i++) {
ul.removeChild(liList[i]);
}

var ul = document.getElementById('demo');
var liList = ul.getElementsByTagName('li');
var lilength = liList.length;
for (var i = 0; i < lilength; i++) {
ul.removeChild(liList[0]);
}