A simple hash table implementation.

hash-table.js

function Map() {
    var dict = {};

    return {
        add_key_value_pair: function(key, value) {
            dict[key] = value;
        },
        get_value: function(key) {
            var val = dict[key];
            if (val === undefined) { 
               throw new Error("Key not found >:|");
            }
            return val;
        },
        remove_key: function(key) { 
            if (dict[key] === undefined) { 
               throw new Error("Key not found >:|");
            } else {
                delete dict[key];
            }
        }
    }
}

function MapList() {
    var list = [];

    return {
        add_key_value_pair: function(key, value) {
            var next = [key, value];
            list.push(next);
        },
        get_value: function(key) {
            var found = list.filter(function(elem) {
                return elem[0] === key;
            }); 
            if (found.length === 0) { 
               throw "Key not found >:|";
            }
            return found[0][1];
        },
        remove_key: function(key) { 
            var found = list.filter(function(elem) {
                return elem[0] !== key;
            }); 
            if (found.length === list.length) { 
               throw "Key not found >:|";
            }
            list = found;
        }
    }
}

//var m = MapList();
//m.add_key_value_pair("0", "apple");
//m.add_key_value_pair("1", "mango");
//var test1 = m.get_value("0") === "apple";
//var test2;
//try { 
//    m.add_key_value_pair("4", "apple");
//    m.remove_key("4");
//    m.get_value("4");
//    test2 = false; 
//} catch (e) {
//    test2 = true;
//}
//
//console.log( "test1: " + test1 + "\ntest2: " + test2 );

function Tree(key,value) {
    var d = [key, value]; 
    var left = null;
    var right = null;

    return {
        add: function(key, value) {
            var k = d[0], v = d[1];

            if (key > k) {
               if (right === null)
                   right = Tree(key, value);
               else
                   right.add(key,value);
            } else if (key < k) {
               if (left === null)
                   left = Tree(key, value);
               else
                   left.add(key,value);
            } else  {
                d = [key, value];
            }
        },
        get: function(key) {
            var k = d[0], v = d[1];

            if (key === k) {
                return v;
            } else if (key > k) {
                if (right === null) {
                    throw "Key not found >:|"
                } else {
                    return right.get(key);
                }
            } else {
                if (left === null) {
                    throw "Key not found >:|"
                } else {
                    return left.get(key);
                }
            }

        },
        remove: function(key) {
            throw "Psych";
        }
    }
}

function MapTree() {
    var bst = null;

    return {
        add_key_value_pair: function(key, value) {
            if (bst === null) 
                bst = Tree(key, value);
            else
                bst.add(key,value);
        },
        get_value: function(key) {
            return bst.get(key);
        },
        remove_key: function(key) { 
            bst.remove(key);
        }
    }
}

(function(n) {
    var m = Map();
    var mL = MapList();
    var mT = MapTree();

    console.log("Adding key value pairs..");
    for(var i = 0; i < n; i++) {
        m.add_key_value_pair(i, "cool");
        mL.add_key_value_pair(i, "cool");
        mT.add_key_value_pair(i, "cool");
    }

    console.log("Timing map..");
    var mStart = new Date();
    for(var i = 0; i < n; i++) {
        m.get_value(i);
    }
    var mEnd = new Date();
    var mDiff = mEnd - mStart;;

    console.log("Timing map list..");
    var mLStart = new Date();
    for(var i = 0; i < n; i++) {
        mL.get_value(i);
    }
    var mLEnd = new Date();
    var mLDiff = mLEnd - mLStart;

    console.log("Timing map tree..");
    var mTStart = new Date();
    for(var i = 0; i < n; i++) {
        mT.get_value(i);
    }
    var mTEnd = new Date();
    var mTDiff = mTEnd - mTStart;

    console.log("Map lookup:     " + mDiff  + "ms");
    console.log("MapList lookup: " + mLDiff + "ms");
    console.log("MapTree lookup: " + mTDiff + "ms");
    console.log("cool");
})(10000);