How can i check every directory in my device in ionic 3

Question

Is there any way we can check directory and files from root directory with loop process in all its sub directories. I found a code but it needs first directory but i need it to be from root directory.

this._storage = cordova.file.externalDataDirectory;
this.file.checkDir(this._storage, 'mydir').then(_ => console.log('yay')).catch(err => console.log('boooh'));