停止拖动后立即重新启动拖动

如何在停止后立即重新启用拖动?

this.layer = new Konva.Layer({draggable : true});

function myPosition() {
     ...
}

var that = this;
this.layer.dragBoundFunc( 
    function(pos) {
        var y = pos.y;
        if (y + myPosition()<0) {
            this.stopDrag();
            setTimeout(function() {that.layer.startDrag();}, 30);
        }
        if (y+myPosition()>50) {
            this.stopDrag();
            setTimeout(function() {that.layer.startDrag();}, 30);
        }               
        return {
            x : this.getAbsolutePosition().x,
            y : y
        };
    });