How to download and save images from web service to app resource folder using Cordova

I am creating Offline mobile app that shows information for some places . I am using local prepopulated sqlite database. There is one update button. When User click on this button ajax call will get fire to update local database by comparing remote database. If there is any new change in remote database then I have to update local database. I don't know how to achieve this also I have to download and save images from web service to app resources folder