joint.all.js
function(ref, distance) {
            var theta = toRad(point(ref).theta(this));
            return this.offset(cos(theta) * distance, -sin(theta) * distance);
        }
function(ref, distance) {
            var theta = toRad(point(ref).theta(this));
            return this.offset(cos(theta) * distance, -sin(theta) * distance);
        }
Move point on line starting from ref ending at me by distance distance.