Having some fun with JavaScript. Quicksort implementation for javascript arrays

QuicksortArray.js

// Helper Constructor
var RandomArray = function(size) {
  size = size || 10;
	var tempArray = [];
	for(var count=0,max = size;count<max;count++) {
		tempArray.push(~~(Math.random()*100));
	}
	return tempArray;
};

// Check to see if the array is sorted
Array.prototype.isSorted = function(){
	var arrayIndex = this.length;
	
	// Typically I would write a for loop for readability
	// But today, we are going for speeeeeeed (yeeeeahhhhhhh)
	while(arrayIndex--) {
    // Gotta catch that edge case!
		if(arrayIndex>0 && this[arrayIndex]<this[arrayIndex-1]) {
			return false;
		}
	}
	return true;
};

Array.prototype.quicksort = function() {
	// Catching the base case of an empty array or a single value
    if(this.length <= 1) {
		return this;
	}
	
	var left =[], // Left Side array, used to store values less than the pivot
		right =[], // Right side array, used to store values greater than the pivot
		pivotArr = [], // PivotArr is to catch the duplicate values.
		pivot; // Since we are in the business of declaring vars, the pivot can live here

  // If its even, then grab the floor(middle), otherwise lets get the real mid!
	if(this.length%2 === 0) {
		pivot = this.length/2;
	} else {
		pivot = (this.length+1)/2;
	}

	for (var i=0, max = this.length;i<max;i++) {
		if(this[i] < this[pivot]) {
			left.push(this[i]);
		} else if(this[i] > this[pivot]) {
			right.push(this[i]);
		} else {
			pivotArr.push(this[i]);
		}
	}
	
	left = left.quicksort(); // Recursively go down
	right = right.quicksort(); // Recursively go down
	
	// Return leftArray + pivotvalueArray + rightArray
	return (left.concat(pivotArr)).concat(right);
};

// Test Cases Helper
function expect(value, expected, message) {
	message = message || "Test case: ";
	if(value !== expected) {
		return message + "false ("+value+" did not match "+expected+")";
	} else {
		return message + "true";
	}
}

(function(){
	console.log("*** Testing Sort Functionality ***");
	console.log(expect([1,2,3].isSorted(), true, "Sorted array is sorted: "));
	console.log(expect([3,2,1].isSorted(), false, "Unsorted array is not sorted: "));
	
	console.log("*** Testing Quicksort ***");
  var temp = new RandomArray();
	var sortedArray = temp.quicksort();	
	console.log("Unsorted: "+temp);
	console.log("Sorted: "+sortedArray);
	console.log(expect(sortedArray.isSorted(), true, "The quicksorted array is sorted: "));	
})();