C++

Call a JavaScript Function Returning an Integer

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

#include <CkStringBuilder.h>
#include <CkJs.h>
#include <CkJsonObject.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.
    CkStringBuilder sbScript;
    success = sbScript.LoadFile("js_call_function.js","utf-8");
    if (success == false) {
        std::cout << sbScript.lastErrorText() << "\r\n";
        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.
    CkJs js;

    CkJsonObject 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.
        std::cout << result.emit() << "\r\n";

        // Also examine the LastErrorText.
        std::cout << js.lastErrorText() << "\r\n";
        return;
    }

    std::cout << result.emit() << "\r\n";

    // 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)

    CkJsonObject funcCall;

    // 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.put_EmitCompact(false);
    std::cout << funcCall.emit() << "\r\n";

    success = js.CallFunction(funcCall,result);
    if (success == false) {
        // Examine the result for an exception.
        std::cout << result.emit() << "\r\n";

        // Also examine the LastErrorText.
        std::cout << js.lastErrorText() << "\r\n";
        return;
    }

    std::cout << result.emit() << "\r\n";

    // Output:

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

    int retval = result.IntOf("value");
    std::cout << "retval = " << retval << "\r\n";
    }