Use below script to list all Lists and its Item Count
var context = SP.ClientContext.get_current();
var lists = context.get_web().get_lists();
context.load(lists, "Include(Title, ItemCount)");
context.executeQueryAsync(success, fail);
function success() {
var maxLength = 0;
var longestTitle = '';
var itemCount = 0;
var enumerator = lists.getEnumerator();
while (enumerator.moveNext()) {
var list = enumerator.get_current();
if(maxLength < list.get_title().length) {
maxLength = list.get_title().length;
longestTitle = list.get_title();
itemCount = list.get_itemCount();
}
}
alert(longestTitle);
alert(itemCount);
}
