Change src of images in library.

Good Evening,

I am currently making an animation that changes as I click buttons. Since it uses heavy raster images I have preloaded them in the cache and I want them to replace a current spritesheet by replacing the src and going back to frame 1.

The getelementbyid method will only read elements in the html. Any ideas on how to change src of images defined in the js?

Any ideas on how to do that.