Javascript Data Structure Tutorial - Javascript Dictionary

function Dictionary() { //  w  w w  .  java  2  s  . c  o  m
    this.datastore = new Array(); 
    this.add = add; 
    this.datastore = new Array(); 
    this.find = find; 
    this.remove = remove; 
    this.showAll = showAll; 
    this.showSorted = showSorted; 
    this.count = count; 
    this.clear = clear;     
} 
//add() function takes two arguments, a key and a 
//value. The key is the index for the value element. Here is the code: 
function add(key, value) { 
    this.datastore[key] = value; 
} 
//find() function takes a key as its argument and 
//returns the value associated with it.
function find(key) { 
    return this.datastore[key]; 
} 

//Removing a key-value pair from a dictionary involves 
//using a built-in JavaScript function: delete. 
//This function is part of the Object class and takes a reference to a key as 
//its argument. 
//The function deletes both the key and the associated value. 
function remove(key) { 
    delete this.datastore[key]; 
} 
function showAll() { 
    for (var key in Object.keys(this.datastore).sort()) { 
        console.log(key + " -> " + this.datastore[key]); 
    } 
} 

function showSorted() { 
    for (var key in Object.keys(this.datastore).sort()) { 
        console.log(key + " -> " + this.datastore[key]); 
    } 
} 

function count() { 
    var n = 0; 
    for (var key in Object.keys(this.datastore)) { 
        ++n; 
    } 
    return n; 
} 
function clear() { 
    for (var key in Object.keys(this.datastore)) { 
        delete this.datastore[key]; 
    } 
} 

var pbook = new Dictionary(); 
pbook.add("A","123"); 
pbook.add("B", "345"); 
pbook.add("C", "456"); 
console.log("B's extension: " + pbook.find("B")); 
pbook.remove("B"); 
pbook.showAll(); 
pbook.showSorted(); 
pbook.clear(); 
console.log("Number of entries: " + pbook.count());