gistfile1.js

constructor(x, y) {
	...
	this.isBeingDragged = false;
	dragger.events.onDragStart.add(this.onDragStart, this);
	dragger.events.onDragStop.add(this.onDragStop, this);
	...
}
onDragStart(){
	this.isBeingDragged = true;
}
onDragStop(){
	this.isBeingDragged = false;
	/* Reset pin and dragger position */
	this.dragger.position.setTo(0, 0);
	this.pin.position.setTo(0, 0);
}
update(){
	if (this.isBeingDragged) {
		var distance  = this.dragger.getMagnitude();
		this.pin.position.copyFrom(this.dragger);
		if (distance > 90) this.pin.setMagnitude(90);
	}
}