如何在ionic/angularjs中预取url ?

I am pretty new to ionic 1 and I am working on an application (with Ionic 1 and angular js) with multiple URLs where each URL brings up a list of categories, followed by a list of items for each category and each item has a document URL. How do I preload all these URLs on launch in the background but not display them?Is there any way this can be achieved? a good code sample or tutorial will help greatly. Also, please let me know if this will be the best approach, as in pre-loading and pre-caching all content upon launch or should it be done category by category or some other way. I am pretty new to ionic 1 and I am working on