joint.all.js
function rect(x, y, w, h) {
        if (!(this instanceof rect))
            return new rect(x, y, w, h);
        if (y === undefined) {
            y = x.y;
            w = x.width;
            h = x.height;
            x = x.x;        
        }
        this.x = x;
        this.y = y;
        this.width = w;
        this.height = h;
    }
function rect(x, y, w, h) {
        if (!(this instanceof rect))
            return new rect(x, y, w, h);
        if (y === undefined) {
            y = x.y;
            w = x.width;
            h = x.height;
            x = x.x;        
        }
        this.x = x;
        this.y = y;
        this.width = w;
        this.height = h;
    }
Rectangle. ----------