C#

Call a JavaScript Function Returning an Integer

See more JavaScript Examples

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

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.
Chilkat.StringBuilder sbScript = new Chilkat.StringBuilder();
success = sbScript.LoadFile("js_call_function.js","utf-8");
if (success == false) {
    Debug.WriteLine(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.
Chilkat.Js js = new Chilkat.Js();

Chilkat.JsonObject result = new Chilkat.JsonObject();
result.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.
    Debug.WriteLine(result.Emit());

    // Also examine the LastErrorText.
    Debug.WriteLine(js.LastErrorText);
    return;
}

Debug.WriteLine(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)

Chilkat.JsonObject funcCall = new Chilkat.JsonObject();

// 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.EmitCompact = false;
Debug.WriteLine(funcCall.Emit());

success = js.CallFunction(funcCall,result);
if (success == false) {
    // Examine the result for an exception.
    Debug.WriteLine(result.Emit());

    // Also examine the LastErrorText.
    Debug.WriteLine(js.LastErrorText);
    return;
}

Debug.WriteLine(result.Emit());

// Output:

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

int retval = result.IntOf("value");
Debug.WriteLine("retval = " + Convert.ToString(retval));