Go

Call a JavaScript Function Returning an Integer

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Demonstrates how to call a JavaScript function that returns an integer. Go

    success := false

    // ----------------------------------------------------------------------------------
    // The Javascript function called in this example is shown at the bottom of this page.
    // -----------------------------------------------------------------------------------

    // In this example, we'll load the Javascript function definition from a file.
    // It doesn't need to come from a file.  It could just as easily be loaded from a string.
    sbScript := chilkat.NewStringBuilder()
    success = sbScript.LoadFile("js_call_function.js","utf-8")
    if success == false {
        fmt.Println(sbScript.LastErrorText())
        sbScript.DisposeStringBuilder()
        return
    }

    // Note: Each instance of a Chilkat Js object automatically establishes
    // its own internal runtime and context.  Applications do not need to explicitly create
    // the JavaScript runtime or context.
    js := chilkat.NewJs()

    result := chilkat.NewJsonObject()
    result.SetEmitCompact(false)

    // Call Eval to add the function (shown at the bottom of this page) to the context's global object
    success = js.Eval(sbScript,result)
    if success == false {
        // Examine the result for an exception.
        fmt.Println(*result.Emit())

        // Also examine the LastErrorText.
        fmt.Println(js.LastErrorText())
        sbScript.DisposeStringBuilder()
        js.DisposeJs()
        result.DisposeJsonObject()
        return
    }

    fmt.Println(*result.Emit())

    // The expected output is "undefined":

    // {
    //   "type": "undefined",
    //   "value": "undefined"
    // }

    //    When Eval processes a script containing only a function declaration,
    //    it successfully performs the action (the function becomes defined).
    //    However, since the script consists of a statement that produces no value,
    //    the script's overall completion value is empty. In JavaScript, the
    //    absence of a value is represented by `undefined`.
    // 
    //    Therefore, the Eval call returns `undefined`.

    // ------------------------------------------------------------------------------
    // Call the function calculateScore("Player1", 10, 20)

    funcCall := chilkat.NewJsonObject()

    // Create JSON defining the function call:

    // {
    //   "name": "calculateScore",
    //   "args": [ "Player1", 10, 20 ]
    // }

    funcCall.UpdateString("name","calculateScore")
    funcCall.UpdateString("args[0]","Player1")
    funcCall.UpdateInt("args[1]",10)
    funcCall.UpdateInt("args[2]",20)

    funcCall.SetEmitCompact(false)
    fmt.Println(*funcCall.Emit())

    success = js.CallFunction(funcCall,result)
    if success == false {
        // Examine the result for an exception.
        fmt.Println(*result.Emit())

        // Also examine the LastErrorText.
        fmt.Println(js.LastErrorText())
        sbScript.DisposeStringBuilder()
        js.DisposeJs()
        result.DisposeJsonObject()
        funcCall.DisposeJsonObject()
        return
    }

    fmt.Println(*result.Emit())

    // Output:

    // {
    //   "type": "int",
    //   "value": 37
    // }

    retval := result.IntOf("value")
    fmt.Println("retval = ", retval)

    sbScript.DisposeStringBuilder()
    js.DisposeJs()
    result.DisposeJsonObject()
    funcCall.DisposeJsonObject()