Create a thumbnail of document after uploading?

I am making a tiny website with reactJS where users can upload documents and share them,since multiple extensions are being uploaded,I managed to make the viewing work by just using google docs viewer. but now i want to have thumbnails of those files,maybe of the first page so that it shows up un the search feature. seeing that theres many extensions flying around i cant figure out how to approach this,what can i use to solve this problem ? thank you.