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This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -0,0 +1,62 @@ // Copyright (C) 2020 Alessandro Segala (ItalyPaleAle) // License: MIT // MyGoFunc fetches an external resource by making a HTTP request from Go // The JavaScript method accepts one argument, which is the URL to request func MyGoFunc() js.Func { return js.FuncOf(func(this js.Value, args []js.Value) interface{} { // Get the URL as argument // args[0] is a js.Value, so we need to get a string out of it requestUrl := args[0].String() // Handler for the Promise // We need to return a Promise because HTTP requests are blocking in Go handler := js.FuncOf(func(this js.Value, args []js.Value) interface{} { resolve := args[0] reject := args[1] // Run this code asynchronously go func() { // Make the HTTP request res, err := http.DefaultClient.Get(requestUrl) if err != nil { // Handle errors: reject the Promise if we have an error errorConstructor := js.Global().Get("Error") errorObject := errorConstructor.New(err.Error()) reject.Invoke(errorObject) return } defer res.Body.Close() // Read the response body data, err := ioutil.ReadAll(res.Body) if err != nil { // Handle errors here too errorConstructor := js.Global().Get("Error") errorObject := errorConstructor.New(err.Error()) reject.Invoke(errorObject) return } // "data" is a byte slice, so we need to convert it to a JS Uint8Array object arrayConstructor := js.Global().Get("Uint8Array") dataJS := arrayConstructor.New(len(data)) js.CopyBytesToJS(dataJS, data) // Create a Response object and pass the data responseConstructor := js.Global().Get("Response") response := responseConstructor.New(dataJS) // Resolve the Promise resolve.Invoke(response) }() // 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) }) }