The Iterator!

basic-iterator.js

// Our iterator
var iterator = (function() {
    
    var index  = -1,
        // Our data
       data = ['joe', 'chapman', 'developer', 'UK'],
        // cache the length
       length = data.length;
    
    return {

        next: function() {
            if (this.hasNext()) {
                index++;
                return data[index];
            }
            return null;
        }, 

        hasNext : function() {
            return index < length-1; 
        }
    };

}());

var list = document.getElementById('list'),
    data = [];

// Testing
while(iterator.hasNext()) {
    data.push('<li>' + iterator.next() + '</li>');
}
  
list.innerHTML = data.join('');