The next Chrome release will support bigints natively in a matter of days.
Node.js is expected to upgrade the V8 soon too.
The major browsers are expected to follow suite.
Rakudo.js is already ready to use that new functionality.
As part of working on making Rakudo.js run in the browser I'm replacing all the node.js dependent stuff.
For some bignum operations we use a node.js binding to OpenSSL, after the pure js alternatives proved incomplete and/or buggy I have decided that it's not worth to spend the effort towards supporting stuff that will be obsolete soon and use the new features.
Obviously if someone needs legacy support he is welcome to work on that (and I'll try my best to help him).