Answers for "deleteall docs in firebase"

how to uninstall firebase

You can type 
$ which firebase 
on the command line and check the location. 
Then 
$ rm <location>

on mac the location is /usr/local/bin/firebase

Or, if you installed firebase through
$ npm install -g firebase-tools

then you should run 
$ npm uninstall -g firebase-tools

how to delete firebase collection

this.db
  .collection('cart')
  .get()
  .toPromise()
  .then((querySnapshot) => {
  querySnapshot.forEach((doc) => {
    doc.ref.delete();
  });
});