/**
	Mutable sqaure type, contains only inuque elements. 
	Depending on the usecases type could be implemented as 
	immutable by removing add methods.
**/
var  UniqueSquare = function(n) {
	//Original idea was to use set (JS object), however it has the same issues 
	//specifying unique order, so decided to go with an array (which maintains order,
	// but is private) and adding public methods to guarantee data consistency (data is unique).
	// It's also easier to use the result (getSquare) in UI templates 
	//(probably AngularJS as well).
	var elements = [];
	var contains = function(element) {
		return ~elements.indexOf(element);	
	};

	return {
		add: function(element) {
			if (elements.length < n*n && !contains(element)) {
				elements.push(element);
			} else {
				// In case it's critical to ensure data is consistent, 
				//depending on use case might be ignored
				if (elements.length >= n*n) {
					throw "OutOfBoundaryException"; 
				}
				if (contains(element)) {
					throw "Element has already been added"; 
				}
			}
		},
		/**
			Adds mutable capabilities (allows to change data), 
			could be overloaded, but's left it for simplicity
		**/
		setByPosition: function(element, position) {
			if (position < n*n && !contains(element)) {
				elements[position] = element;
			} else {
				if (position >= n*n)
					throw "OutOfBoundaryException";
				if (contains(element)) {
					throw "Element has already been added";
				}
			}
		},
		/**
			Adds mutable capabilities (allows to change data), 
			could be overloaded, but's left it for simplicity
		**/
		set: function(element, x, y) {
			this.setByPosition(element, x*n + y);	
		},
		/**
			Read only data to be used by UI templates to display it.
		**/
		getSquare: function() {
			var result = [];
			// result / source data also could be modified to store position (e.g [{value: 0, x: 0, y:1},...])
			// hdepends on the use case (it's always can be easily calculated).
			var data = elements.slice(0);
			while (data.length > 0)
    			result.push(data.splice(0, n));
    		return result;
		}
	};
};


var x = new UniqueSquare(2);
x.add(3);
x.add(2);
x.add(4);
x.add(5);
x.getSquare();
x.set(6,1,1) // if we need to modify the Square
x.getSquare();