function HashTable() 
{ 
var size = 0; 
var entry = new Object(); 
this.add = function (key , value) 
{ 
if(!this.containsKey(key)) 
{ 
size ++ ; 
} 
entry[key] = value; 
} 
this.getValue = function (key) 
{ 
return this.containsKey(key) ? entry[key] : null; 
} 
this.remove = function ( key ) 
{ 
if( this.containsKey(key) && ( delete entry[key] ) ) 
{ 
size --; 
} 
} 
this.containsKey = function ( key ) 
{ 
return (key in entry); 
} 
this.containsValue = function ( value ) 
{ 
for(var prop in entry) 
{ 
if(entry[prop] == value) 
{ 
return true; 
} 
} 
return false; 
} 
this.getValues = function () 
{ 
var values = new Array(); 
for(var prop in entry) 
{ 
values.push(entry[prop]); 
} 
return values; 
} 
this.getKeys = function () 
{ 
var keys = new Array(); 
for(var prop in entry) 
{ 
keys.push(prop); 
} 
return keys; 
} 
this.getSize = function () 
{ 
return size; 
} 
this.clear = function () 
{ 
size = 0; 
entry = new Object(); 
} 
}