Is WebAssembly faster than vanilla Javascript?

I keep seeing GitHub issues of people just like me trying to figure out what WebAssembly (Wasm) and previouslyasm.js mean for performance-related javascript (in my case, games). WebAssembly should introduce less abstraction between you and the hardware and so your code should in general run faster, right? In reality this question is harder to answer because WebAssembly runs in a Javascript VM-like environment and was not made directly motivated for performance. I'll be putting aside the misinformation and anecdotes to hopefully find out if and how applying Wasm might make your projects more performant.

A bit of background