ordered_hm.js

     /*
      * Simple hash map using javascript objects and an ordered array.
      * Repeated elements are not allowed.
      *  
      * @param sort_method By default is ASC order, but you can specified whatever you want.
      *
      * The public methods are:
      *     -set
      *     -get
      *     -del
      *     -foreach
      * next step: Try to improve the insert method
      */
     var HashMap = function (sort_method){
        var data = {};
        var order_keys = [];
        var default_sort =  function(a,b) {
            return a < b;
        };
        var sort = sort_method || default_sort;

        /*
         * Insert the new key using the sort method.
         */
        function insert(key) {
            var len = order_keys.length;
            if (len == 0) {
                order_keys.push(key);
            } else {
                for (i = 0; i < len; i++) {
                    if (sort(key, order_keys[i])) {
                        if (order_keys[i-1] != key) { /* the element is not repeated */
                            order_keys.splice(i,0, key); 
                        }
                        break;
                    }
                }
                if ( i== len) {
                     order_keys.splice(i,0, key); 
                }
            }
        }

        function binarySearch(a, value, low, high) {
               if (high < low)
                   return -1 // not found
               mid = parseInt(low + (high - low) / 2)
               if (a[mid] > value)
                   return binarySearch(a, value, low, mid-1)
               else if (a[mid] < value)
                   return binarySearch(a, value, mid+1, high)
               else
                   return mid // found
        }
         
        function del(key) {
            delete data[key];
            var index = binarySearch(order_keys, key, 0, order_keys.length);
            if (index > -1) order_keys.splice(index,1);       
        }

        function set(key, value) {
            data[key] = value;
            insert(key);
        }

        function get(key) {
            return data[key];
        }

        /*
         * Executes a specified function on each ordered element of the array;
         * Stop if the callback returns false
         */
        function foreach(callback) {
            var len = order_keys.length;
            for (var i = 0; i < len; i++) {
                if (callback(order_keys[i], data[order_keys[i]]) === false) break;
            }
        }
        
        return {set:set, get:get, foreach:foreach, del:del};
     }