BarCode scanner Issue

For some reason, when I click the button to scan something, it comes up undefined. I followed this tutorial:

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjC0pj6ttPuAhXhct8KHV0HDkEQFjAAegQIARAC&url=https%3A%2F%2Fdocs.thunkable.com%2Fbarcode-scanner&usg=AOvVaw1reAHtbmCVNYWp3g24A73a