Ionic 3 file uploading from filechooser to firebase storage

Ionic Framework ionic-v3
1

I’m trying to upload a pdf from ionic 3 app to firebase. by using this method I can upload a text file by just creating them.

uploadToStorage(information):AngularFireUploadTask
  {
    let newName = `${new Date().getTime()}.txt`;
    return this.afST.ref(`files/${newName}`).putString(information);

  }

here is the place where i call the function

uploadInfo(text)
  {
    let upload = this.dataProvider.uploadToStorage(text);

    upload.then(res=>{
      console.log('res',res);
      this.dataProvider.storeInfoOnDatabase(res.metadata,text).then(()=>{
        let toast = this.toastCtrl.create({
          message : 'New File Added',
          duration: 3000
        });
        toast.present();
      });
    });
  }

what i need to do is how i expand the uploadstorage() function to upload a file getting from ionic file chooser??