You're off to a great start. +1 for providing comments.
Here are some tips:
##1) Define variables before modifying them.
So the constants MAX_HEAP and MIN_HEAP should be defined after PriorityQueue.
Old Code:
PriorityQueue.MAX_HEAP = 0;
PriorityQueue.MIN_HEAP = 1;
function PriorityQueue(criteria, heapType) {
//...
}
New Code:
function PriorityQueue(criteria, heapType) {
//...
}
PriorityQueue.MAX_HEAP = 0;
PriorityQueue.MIN_HEAP = 1;
Side note: In shiftHighestPriorityElement(), _queue isn't defined. I think it should be queue.
##2) Use this to attach attributes to a Constructor.
More info
Example: Old Code:
//..
function PriorityQueue(criteria, heapType) {
this.length = 0;
var queue = [];
var isMax = false;
//...
New Code:
//..
function PriorityQueue(criteria, heapType) {
this.length = 0;
this.queue = [];
this.isMax = false;
//...
##3) Split up functions longer than 8 - 12 lines of code into smaller functions. Use the prototype on an object to attach functions to the constructor instead of including all the functionality within.
Old Code:
function PriorityQueue(criteria, heapType) {
//...
this.insert = function (value) {
if (!value.hasOwnProperty(criteria)) {
throw "Cannot insert " + value + " because it does not have a property by the name of " + criteria + ".";
}
queue.push(value);
length++;
bubbleUp(length - 1);
}
//...
var swap = function (self, target) {
var placeHolder = queue[self];
queue[self] = queue[target];
queue[target] = placeHolder;
}
//...
}
New Code:
function PriorityQueue(criteria, heapType) {
//...
}
PriorityQueue.prototype.insert = function (value) {
if (!value.hasOwnProperty(this.criteria)) {
throw "Cannot insert " + value + " because it does not have a property by the name of " + this.criteria + ".";
}
this.queue.push(value);
this.length++;
this.bubbleUp(this.length - 1);
}
PriorityQueue.prototype.swap = function (self, target) {
var placeHolder = this.queue[self];
this.queue[self] = this.queue[target];
this.queue[target] = placeHolder;
}
##4) Sometimes it's better to just return an boolean expression.
Old Code:
if (queue[self][criteria] < queue[target][criteria]) {
return true;
} else {
return false;
}
New Code:
return (queue[self][criteria] < queue[target][criteria]);
##5) Make sure to create test units. Try out qunit.js
##6) Simplify if and else conditions.
Old Code:
var isMax = false;
//Constructor
if (heapType==PriorityQueue.MAX_HEAP) {
isMax = true;
} else if (heapType==PriorityQueue.MIN_HEAP) {
isMax = false;
} else {
throw heapType + " not supported.";
}
New Code:
this.isMax = !!heapType;
if ( heapType !== 0 || heapType !== 1 ){
throw heapType + " not supported.";
}
##7) Use === instead of == when comparing for value and type of primitive values.
Old code:
} else if (value == 0) {
New Code:
} else if (value === 0) {
Or
} else if (!value) {
##Final code:
function PriorityQueue(criteria, heapType) {
this.criteria = criteria;
this.length = 0;
this.queue = [];
this.isMax = !!heapType;
if ( heapType !== 0 || heapType !== 1 ){
throw heapType + " not supported.";
}
}
PriorityQueue.prototype.insert = function (value) {
if (!value.hasOwnProperty(this.criteria)) {
throw "Cannot insert " + value + " because it does not have a property by the name of " + this.criteria + ".";
}
this.queue.push(value);
this.length++;
this.bubbleUp(this.length - 1);
};
PriorityQueue.prototype.getHighestPriorityElement = function () {
return this.queue[0];
};
PriorityQueue.prototype.shiftHighestPriorityElement = function () {
if (length < 0) {
throw("There are no more elements in your priority queue.");
}
var oldRoot = this.queue[0];
var newRoot = this.queue.pop();
this.length--;
this.queue[0] = newRoot;
this.swapUntilQueueIsCorrect(0);
return oldRoot;
};
PriorityQueue.prototype.bubbleUp = function (index) {
if (index === 0) {
return;
}
var parent = this.getParentOf(index);
if (this.evaluate(index, parent)) {
this.swap(index, parent);
this.bubbleUp(parent);
} else {
return;
}
};
PriorityQueue.prototype.swapUntilQueueIsCorrect = function (value) {
var left = this.getLeftOf(value),
right = this.getRightOf(value);
if (this.evaluate(left, value)) {
this.swap(value, left);
this.swapUntilQueueIsCorrect(left);
} else if (this.evaluate(right, value)) {
this.swap(value, right);
this.swapUntilQueueIsCorrect(right);
} else if (value === 0) {
return;
} else {
this.swapUntilQueueIsCorrect(0);
}
};
PriorityQueue.prototype.swap = function (self, target) {
var placeHolder = this.queue[self];
this.queue[self] = this.queue[target];
this.queue[target] = placeHolder;
};
PriorityQueue.prototype.evaluate = function (self, target) {
if (this.queue[target] === null || this.queue[self] === null) {
return false;
}
if (this.isMax) {
return (this.queue[self][this.criteria] > this.queue[target][this.criteria]);
} else {
return (this.queue[self][this.criteria] < this.queue[target][this.criteria]);
}
};
PriorityQueue.prototype.getParentOf = function (index) {
return Math.floor(index / 2) - 1;
};
PriorityQueue.prototype.getLeftOf = function (index) {
return index * 2 + 1;
};
PriorityQueue.prototype.getRightOf = function (index) {
return index * 2 + 2;
};
PriorityQueue.MAX_HEAP = 0;
PriorityQueue.MIN_HEAP = 1;
default