Use regular CSS selectors

[bejohu]

Use CSS selectors rather than IDs, e.g.

...
var options = {
  item: '#list-item'
};

var userList = new List('#users', options);
...

[binarykiwi]

You can use an element if you do not want to use an ID:

new List(id/element, options, values);

But yes, would sometimes be easier using a CSS selector.