If your HTML only only one UL Tag as your sample code, this will work for you. else you need to modify it according to your need
var ul = document.getElementsByTagName('ul');
var li = ul[0].getElementsByTagName('li');
var array = new Array();
for (var i = 0; i < li.length; i++) {
array.push(li[i].innerText)
}
alert(array);