Unicode C++

Call a JavaScript Function Returning an Integer

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Demonstrates how to call a JavaScript function that returns an integer. Unicode C++

#include <CkStringBuilderW.h>
#include <CkJsW.h>
#include <CkJsonObjectW.h>

void ChilkatSample(void)
    {
    bool 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.
    CkStringBuilderW sbScript;
    success = sbScript.LoadFile(L"js_call_function.js",L"utf-8");
    if (success == false) {
        wprintf(L"%s\n",sbScript.lastErrorText());
        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.
    CkJsW js;

    CkJsonObjectW result;
    result.put_EmitCompact(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.
        wprintf(L"%s\n",result.emit());

        // Also examine the LastErrorText.
        wprintf(L"%s\n",js.lastErrorText());
        return;
    }

    wprintf(L"%s\n",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)

    CkJsonObjectW funcCall;

    // Create JSON defining the function call:

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

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

    funcCall.put_EmitCompact(false);
    wprintf(L"%s\n",funcCall.emit());

    success = js.CallFunction(funcCall,result);
    if (success == false) {
        // Examine the result for an exception.
        wprintf(L"%s\n",result.emit());

        // Also examine the LastErrorText.
        wprintf(L"%s\n",js.lastErrorText());
        return;
    }

    wprintf(L"%s\n",result.emit());

    // Output:

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

    int retval = result.IntOf(L"value");
    wprintf(L"retval = %d\n",retval);
    }