We just released pako https://github.com/nodeca/pako , port of zlib to javascript. I think that's now the fastest js implementation of deflate / inflate / gzip / ungzip. Also, it has democratic MIT licence. Pako supports all zlib options and it's results are binary equal.
Example:
var inflate = require('pako/lib/inflate').inflate;
var text = inflate(zipped, {to: 'string'});