WebAssembly Instance: Javascript behavior when calling exported functions

Question

When I call an exported function of a WebAssembly module instance, how do Javascript and WebAssembly interact?

instance = WebAssembly.instantiate(bytes)
result = instance.exports.myFunction()

What happens if the .wasm instance enters an infinite loop? Will control eventually be transferred back to the Javascript function that invoked it?

ColinE · Accepted Answer · 2018-08-16 19:29:07Z

5

WebAssembly and JavaScript execute on the same thread. When a JS function invokes an exported wasm function, it yields execution. It only resumes when the wasm function returns. If the wasm function is an infinite loop, your JS code will not be re-entered.

answered Aug 16, 2018 at 19:29

ColinE

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2 Comments

2080 Over a year ago

Does WebAssembly execution block all other asynchronous Javascript functions until it is terminated?

ColinE Over a year ago

When WebAssembly is being executed, asynchronous JS calls will continue to execute (e.g. webworkers, HTTP requests), but any callbacks / return handlers will not be invoked until the WebAssembly function returns.

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