Looks like it depends on https://github.com/nodeca/pako for the zlib compression.

> Almost as fast in modern JS engines as C implementation (see benchmarks).

Impressive, although "almost" is doing some heavy lifting there.

> deflate-pako x 10.22 ops/sec ±0.33% (29 runs sampled)

> deflate-zlib x 18.48 ops/sec ±0.24% (48 runs sampled)

> inflate-pako x 134 ops/sec ±0.66% (83 runs sampled)

> inflate-zlib x 402 ops/sec ±0.74% (87 runs sampled)