Help for encoding audio/video into different format...

[ajenkul]

I'm using ffmpeg in C for my Android project. It works perfect till Google release lasted NDK, all my library broken now.
Then I decided to switch my project to hybrid app, using javascript as a development.
I found this repo which help me decode/encode audio/video file.
The problem is, I have a lot of audio/video encoded by my algorithm, now I want to use ffmpeg in javascript to decode it before it can play in the browser.
Please give me some suggestion, thanks you!