Rectangle Class

gistfile1.js

function Rectangle(left, top, width, height) {
    this.left = left;
    this.top = top;
    this.width = width;
    this.height = height;
    this._computeCorners();
}

Rectangle.prototype._computeCorners = function() {
    this.bottom = this.top + this.height;
    this.right = this.left + this.width;

    this.lt = this.tl = {left:this.left, top:this.top};
    this.ct = this.tc = {left:this.left + this.width / 2, top:this.top};
    this.rt = this.tr = {left:this.left + this.width, top:this.top};

    this.lc = this.cl = {left:this.left, top:this.top + this.height / 2};
    this.c = this.cc = {left:this.left + this.width / 2, top:this.top + this.height / 2};
    this.rc = this.cr = {left:this.left + this.width, top:this.top + this.height / 2};

    this.lb = this.bl = {left:this.left, top:this.top + this.height};
    this.cb = this.bc = {left:this.left + this.width / 2, top:this.top + this.height};
    this.rb = this.br = {left:this.left + this.width, top:this.top + this.height};
};

Rectangle.prototype.isAbove = function(rect) {
    return this.bottom < rect.top;
};

Rectangle.prototype.isBelow = function(rect) {
    return this.top > rect.bottom;
};

Rectangle.prototype.isRight = function(rect) {
    return this.left > rect.right;
};

Rectangle.prototype.isLeft = function(rect) {
    return this.right < rect.left;
};

Rectangle.prototype.overlaps = function(rect) {
    var noOverlap = this.isAbove(rect) || this.isBelow(rect)
                || this.isRight(rect) || this.isLeft(rect);
    return !noOverlap;
};

Rectangle.prototype.translate = function(deltaX, deltaY) {
    return new Rectangle(this.left + deltaX, this.top + deltaY, this.width, this.height);
};

Rectangle.prototype.translatePoint = function(pointName, thatRect, thatPoint) {
    var thisPoint = this[pointName];
    var thatPoint = thatRect[thatPoint];

    //without any further translation, the top-left of the source will get aligned to target
    var translate = {
        left: this.left - thisPoint.left,
        top: this.top - thisPoint.top
    };
    return new Rectangle(thatPoint.left + translate.left, thatPoint.top + translate.top, this.width, this.height);
};