Recently, I want to create a QR Code Scanner with Ionic React. So I found the library: barcode scanner, a great library, the scan speed is very fast and also easy to use. But the problem is that it doesn’t work very well in Ionic React. 

The reason is Ionic use Web component, so If you use Ionic React, than you have to access its shadow dom to manipulate the background css.  So I did a youtube video to show you how to do that.