index.js
function(p) {
        var dx = p.x - this.x,
            dy = p.y - this.y;
        return dx * dx + dy * dy;
    }
function(p) {
        var dx = p.x - this.x,
            dy = p.y - this.y;
        return dx * dx + dy * dy;
    }
Calculate the distance from this point to another point,
without the square root step. Useful if you're comparing
relative distances.
@param {Point} p the other point
@return {Number} distance