Vector2.js

var Vector2 = function(x, y) {
    this.x = x || 0;
    this.y = y || 0;
};
Vector2.prototype = {
    reset: function(x, y) {
        this.x = x;
        this.y = y;
        return this;
    },
    toString: function(decPlaces) {
        decPlaces = decPlaces || 3;
        var scalar = Math.pow(10, decPlaces);
        return "[" + Math.round(this.x * scalar) / scalar + ", " + Math.round (this.y * scalar) / scalar + "]";
    },
    clone: function() {
        return new Vector2(this.x, this.y);
    },
    copyTo: function(v) {
        v.x = this.x;
        v.y = this.y;
    },
    copyFrom: function(v) {
        this.x = v.x;
        this.y = v.y;
    },
    magnitude: function() {
        return Math.sqrt((this.x * this.x) + (this.y * this.y));
    },
    magnitudeSquared: function() {
        return (this.x * this.x) + (this.y * this.y);
    },
    normalise: function() {
        var m = this.magnitude();
        this.x = this.x / m;
        this.y = this.y / m;
        return this;
    },
    reverse: function() {
        this.x =- this.x;
        this.y =- this.y;
        return this;
    },
    plusEq: function(v) {
        this.x += v.x;
        this.y += v.y;
        return this;
    },
    plusNew: function(v) {
        return new Vector2(this.x + v.x, this.y + v.y);
    },
    minusEq: function(v) {
        this.x -= v.x;
        this.y -= v.y;
        return this;
    },
    minusNew: function(v) {
        return new Vector2(this.x - v.x, this.y - v.y);
    },
    multiplyEq: function(scalar) {
        this.x*=scalar;
        this.y*=scalar;
        return this;
    },
    multiplyNew: function(scalar) {
        var returnvec = this.clone();
        return returnvec.multiplyEq(scalar);
    },
    divideEq: function(scalar) {
        this.x/=scalar;
        this.y/=scalar;
        return this;
    },
    divideNew: function(scalar) {
        var returnvec = this.clone();
        return returnvec.divideEq(scalar);
    },
    dot: function(v) {
        return (this.x * v.x) + (this.y * v.y);
    },
    angle: function(useRadians) {
        return Math.atan2(this.y, this.x) * (useRadians ? 1 : Vector2Const.TO_DEGREES);
    },
    rotate: function(angle, useRadians) {
        var cosRY = Math.cos(angle * (useRadians ? 1 : Vector2Const.TO_RADIANS));
        var sinRY = Math.sin(angle * (useRadians ? 1 : Vector2Const.TO_RADIANS));
        Vector2Const.temp.copyFrom(this);
        this.x = (Vector2Const.temp.x * cosRY) - (Vector2Const.temp.y * sinRY);
        this.y = (Vector2Const.temp.x * sinRY) + (Vector2Const.temp.y * cosRY);
        return this;
    },
    equals: function(v) {
        return ((this.x == v.x) && (this.y == v.x));
    },
    isCloseTo: function(v, tolerance) {
        if (this.equals(v))
            return true;
        Vector2Const.temp.copyFrom(this);
        Vector2Const.temp.minusEq(v);
        return (Vector2Const.temp.magnitudeSquared() < tolerance * tolerance);
    },
    rotateAroundPoint: function(point, angle, useRadians) {
        Vector2Const.temp.copyFrom(this);
        Vector2Const.temp.minusEq(point);
        Vector2Const.temp.rotate(angle, useRadians);
        Vector2Const.temp.plusEq(point);
        this.copyFrom(Vector2Const.temp);
    },
    isMagLessThan: function(distance) {
        return (this.magnitudeSquared() < distance * distance);
    },
    isMagGreaterThan: function(distance) {
        return (this.magnitudeSquared() > distance * distance);
    }
};
Vector2Const = {
    TO_DEGREES: 180 / Math.PI,
    TO_RADIANS: Math.PI / 180,
    temp: new Vector2()
};