Cannot get Internal Storage permission at Run Time

[AkashRajpurohit]

The code works fine but the only issue is that i am saving those files on the device internal storage but i have to manually give the permission of accessing the Storage.
Is there any way to give permissions at run time?

P.S - I have tried cordova.Diagnostic plugin but there is no option to ask permission for internal storage.It does have one for external Storage but that piece of code doesn't seems to work