ol.interaction.DragBox Render does not work in latest openlayers

Before I had code like below. This does not work in latest Openlayers. this.boxInteraction.box_ is undefined

/* Flag indicating whether the postcompose listener should raw the "mask" on the map. */
this.drawMask = false;

/* Create a drag box interaction that sets drawMask to true n "boxstart" and sets drawMask to false on "boxend". */
this.boxInteraction = new ol.interaction.DragBox({
	condition: ol.events.condition.shiftKeyOnly,
	className: 'ol-zoombox'
});

this.boxInteraction.on('boxstart', function (e) {
	me.drawMask = true;
});
this.boxInteraction.on('boxend', function (e) {
	me.drawMask = false;
	var map = me.map;
	var view = me.map.getView();
	var extent = e.target.getGeometry().getExtent();
	var size = map.getSize();

	var resolution = view.getConstrainedResolution(view.getResolutionForExtent(extent, size));

	var center = ol.extent.getCenter(extent);
	if (view.constrainCenter && typeof view.constrainCenter !== 'undefined') center = view.constrainCenter(center);

	view.animate({
		resolution: resolution,
		center: center,
		duration: 200,
		easing: ol.easing.easeOut
	});
});
/* ****** ERROR ON LINE BELOW ****** */
if (typeof Object.getPrototypeOf(this.boxInteraction.box_) === 'undefined') {
	Object.setPrototypeOf(this.boxInteraction.box_, Object.getOwnPropertyNames(Object.getPrototypeOf(this.boxInteraction.box_)));
}
Object.getPrototypeOf(this.boxInteraction.box_).render_ = function () {
	var startPixel = this.startPixel_;
	var endPixel = this.endPixel_;
	var px = 'px';
	var style = this.element_.style;
	style.left = Math.min(startPixel[0], endPixel[0]) + px;
	style.top = Math.min(startPixel[1], endPixel[1]) + px;
	style.width = Math.abs(endPixel[0] - startPixel[0]) + px;
	style.height = Math.abs(endPixel[1] - startPixel[1]) + px;
	if (this.map_ && this.startPixel_ && this.endPixel_) {
		this.map_.render();
	}
};

[M393]

If you can’t use modules directly in your project you can make your own custom build which will also be a lot smaller. See https://github.com/phpmyadmin/phpmyadmin/pull/16959 for an example

[ahocevar]

So, for everyone wanting to use private members at their own risk: use the ol package instead of the legacy build, then you won’t run into this issue. No-one should be using the legacy build in production anyway.