It's part of the Atomics feature set (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics/wait https://developer.mozilla.or

It's part of the Atomics feature set (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics/wait https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...). You have a shared chunk of memory and you say "please sleep until this memory changes". Then it's up to the host to change that memory.