vector.js

function Vector(x, y, z) {
	this.x = x || 0;
	this.y = y || 0;
	this.z = z || 0;
}
Vector.prototype = {
	negative: function() {
		return new Vector(-this.x, -this.y, -this.z);
	},
	add: function(v) {
		if (v instanceof Vector)
			return new Vector(this.x + v.x, this.y + v.y, this.z + v.z);
		else return new Vector(this.x + v, this.y + v, this.z + v);
	},
	subtract: function(v) {
		if (v instanceof Vector)
			return new Vector(this.x - v.x, this.y - v.y, this.z - v.z);
		else return new Vector(this.x - v, this.y - v, this.z - v);
	},
	multiply: function(v) {
		if (v instanceof Vector)
			return new Vector(this.x * v.x, this.y * v.y, this.z * v.z);
		else return new Vector(this.x * v, this.y * v, this.z * v);
	},
	divide: function(v) {
		if (v instanceof Vector)
			return new Vector(this.x / v.x, this.y / v.y, this.z / v.z);
		else return new Vector(this.x / v, this.y / v, this.z / v);
	},
	equals: function(v) {
		return this.x == v.x && this.y == v.y && this.z == v.z;
	},
	dot: function(v) {
		return this.x * v.x + this.y * v.y + this.z * v.z;
	},
	cross: function(v) {
		return new Vector(
			this.y * v.z - this.z * v.y,
			this.z * v.x - this.x * v.z,
			this.x * v.y - this.y * v.x
		);
	},
	get length() {
		return Math.sqrt(this.dot(this));
	},
	get length2() {
		return this.dot(this);
	},
	unit: function() {
		return this.divide(this.length);
	},
	get min() {
		return Math.min(Math.min(this.x, this.y), this.z);
	},
	get max() {
		return Math.max(Math.max(this.x, this.y), this.z);
	},
	toAngles: function() {
		return {
			theta: Math.atan2(this.z, this.x),
			phi: Math.asin(this.y / this.length)
		};
	},
	angleTo: function(a) {
		return Math.acos(this.dot(a) / (this.length * a.length));
	},
	toArray: function(n) {
		return [this.x, this.y, this.z].slice(0, n || 3);
	},
	clone: function() {
		return new Vector(this.x, this.y, this.z);
	},
	set: function(x, y, z) {
		this.x = x;
		this.y = y;
		this.z = z;
		return this;
	}
};

//static vector class methods
Vector.negative = function(a, b) {
	b.x = -a.x;
	b.y = -a.y;
	b.z = -a.z;
	return b;
};
Vector.add = function(a, b, c) {
	if (b instanceof Vector) {
		c.x = a.x + b.x;
		c.y = a.y + b.y;
		c.z = a.z + b.z;
	} else {
		c.x = a.x + b;
		c.y = a.y + b;
		c.z = a.z + b;
	}
	return c;
};
Vector.subtract = function(a, b, c) {
	if (b instanceof Vector) {
		c.x = a.x - b.x;
		c.y = a.y - b.y;
		c.z = a.z - b.z;
	} else {
		c.x = a.x - b;
		c.y = a.y - b;
		c.z = a.z - b;
	}
	return c;
};
Vector.multiply = function(a, b, c) {
	if (b instanceof Vector) {
		c.x = a.x * b.x;
		c.y = a.y * b.y;
		c.z = a.z * b.z;
	} else {
		c.x = a.x * b;
		c.y = a.y * b;
		c.z = a.z * b;
	}
	return c;
};
Vector.divide = function(a, b, c) {
	if (b instanceof Vector) {
		c.x = a.x / b.x;
		c.y = a.y / b.y;
		c.z = a.z / b.z;
	} else {
		c.x = a.x / b;
		c.y = a.y / b;
		c.z = a.z / b;
	}
	return c;
};
Vector.cross = function(a, b, c) {
	c.x = a.y * b.z - a.z * b.y;
	c.y = a.z * b.x - a.x * b.z;
	c.z = a.x * b.y - a.y * b.x;
	return c;
};
Vector.unit = function(a, b) {
	var length = a.length;
	b.x = a.x / length;
	b.y = a.y / length;
	b.z = a.z / length;
	return b;
};
Vector.fromAngles = function(theta, phi) {
	return new Vector(
		Math.cos(theta) * Math.cos(phi),
		Math.sin(phi),
		Math.sin(theta) * Math.cos(phi)
	);
};
Vector.randomDirection = function() {
	return Vector.fromAngles(
		Math.random() * Math.PI * 2,
		Math.asin(Math.random() * 2 - 1)
	);
};
Vector.min = function(a, b) {
	return new Vector(Math.min(a.x, b.x), Math.min(a.y, b.y), Math.min(a.z, b.z));
};
Vector.max = function(a, b) {
	return new Vector(Math.max(a.x, b.x), Math.max(a.y, b.y), Math.max(a.z, b.z));
};
Vector.lerp = function(a, b, fraction) {
	return b
		.subtract(a)
		.multiply(fraction)
		.add(a);
};
Vector.fromArray = function(a) {
	return new Vector(a[0], a[1], a[2]);
};
Vector.angleBetween = function(a, b) {
	return a.angleTo(b);
};