This example demonstrates the Vector.normalize() method.

Two lines follow the mouse-cursor, but the thick orange one is limited to the radius of the circle by using normalize().multiply(circleRadius) on the direction Vector computed from the difference of the current cursor position and the circle center.

line.actions.addAction(function() {
    let dir = this.malkasten.pointer
                .subtract(this.position)
                .normalize();

    this.to = this.position.add(
        dir.multiply(c1.radius - c1.options.lineWidth)
    );
});