Golang's syscall/js js.NewCallback is undefined

Question

I am new to both go and wasm and it looks like these projects are pretty fast moving. I was reading an introduction to using wasm in go and it seems although it was written in January, its already out of date.

I am attempting to call a single go function when a JavaScript function is invoked. The example says to do something like this:

 js.Global().Set("jsFunctionName", js.NewCallback(goCallback))

Although when I am trying to compile this, I am getting this error:

./webassembly.go:54:35: undefined: js.NewCallback

I checked the documentation and see no reference to NewCallback. What is the current "correct" way that this should be done?

Answer 1

js.Global().Set("jsFunctionName", js.NewCallback(goCallback))

should be as:

js.Global().Set("jsFunctionName", js.FuncOf(goCallback))

Note the signature of goCallback has changed and now since Go 1.12, there is a support for return values. For example, here is how to expose a simple add function:

// function definition
func add(this js.Value, i []js.Value) interface{} {
  return js.ValueOf(i[0].Int()+i[1].Int())
}

// exposing to JS
js.Global().Set("add", js.FuncOf(add))