Computation intensive applications can be done in multithread by easily using web workers. It is been around for a long time. See the following site for a quick benchmark. [1]
Here are my results:
8 Workers, Test: 2^1024000000 mod 97777 = 20631, 1515 ms
4 Workers, Test: 2^1024000000 mod 97777 = 20631, 2899 ms
2 Workers, Test: 2^1024000000 mod 97777 = 20631, 5773 ms
1 Worker, Test: 2^1024000000 mod 97777 = 20631, 11508 ms
[1]: http://pmav.eu/stuff/javascript-webworkers/
Here are my results: 8 Workers, Test: 2^1024000000 mod 97777 = 20631, 1515 ms 4 Workers, Test: 2^1024000000 mod 97777 = 20631, 2899 ms 2 Workers, Test: 2^1024000000 mod 97777 = 20631, 5773 ms 1 Worker, Test: 2^1024000000 mod 97777 = 20631, 11508 ms