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ItalyPaleAle/js-promise-with-errors-from-wasm.go

Last active October 7, 2020 03:36
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Revisions

  1. ItalyPaleAle revised this gist Oct 7, 2020. No changes.
  2. ItalyPaleAle created this gist Oct 7, 2020.
    42 changes: 42 additions & 0 deletions js-promise-with-errors-from-wasm.go
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,42 @@
    // Copyright (C) 2020 Alessandro Segala (ItalyPaleAle)
    // License: MIT

    // MyGoFunc returns a Promise that fails with an exception about 50% of times
    func MyGoFunc() js.Func {
    return js.FuncOf(func(this js.Value, args []js.Value) interface{} {
    // Handler for the Promise
    handler := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
    resolve := args[0]
    reject := args[1]

    // Run this code asynchronously
    go func() {
    // Cause a failure 50% of times
    if rand.Int()%2 == 0 {
    // Invoke the resolve function passing a plain JS object/dictionary
    resolve.Invoke(map[string]interface{}{
    "message": "Hooray, it worked!",
    "error": nil,
    })
    } else {
    // Assume this were a Go error object
    err := errors.New("Nope, it failed")

    // Create a JS Error object and pass it to the reject function
    // The constructor for Error accepts a string,
    // so we need to get the error message as string from "err"
    errorConstructor := js.Global().Get("Error")
    errorObject := errorConstructor.New(err.Error())
    reject.Invoke(errorObject)
    }
    }()

    // The handler of a Promise doesn't return any value
    return nil
    })

    // Create and return the Promise object
    promiseConstructor := js.Global().Get("Promise")
    return promiseConstructor.New(handler)
    })
    }