Microsoft Office integration in an application

[Adonis4000]

Hello,
I want to make an application that has integrated microsoft office word, excel, outlook etc.
How would I go about doing that? I found there is the Office Common Javascript API so i was thinking of making the application using the React library in JS, but I'm not sure if that provides what I want for my application.
To be clear, I want my users to be able to access their emails from outlook from within my app, and also be able to create word (excel, powerpoint etc.) documents from within my app.

 

Is the javascript api what I am looking for? I there something better for my needs? Am I restricted to the use of javascript to make my application?

It is worth noting I plan to make the application useable on multiple platforms, so at the moment I am considering making it as a web application so the back end can be the same for any platform (windows, android, ios, mac (maybe linux as well)).

Any advice would be greatly appreciated.