Xojo Plugin

Call a JavaScript Function Returning an Integer

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

Dim success As Boolean
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.
Dim sbScript As New Chilkat.StringBuilder
success = sbScript.LoadFile("js_call_function.js","utf-8")
If (success = False) Then
    System.DebugLog(sbScript.LastErrorText)
    Return
End If

//  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.
Dim js As New Chilkat.Js

Dim result As 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) Then
    //  Examine the result for an exception.
    System.DebugLog(result.Emit())

    //  Also examine the LastErrorText.
    System.DebugLog(js.LastErrorText)
    Return
End If

System.DebugLog(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)

Dim funcCall As New Chilkat.JsonObject

//  Create JSON defining the function call:

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

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

funcCall.EmitCompact = False
System.DebugLog(funcCall.Emit())

success = js.CallFunction(funcCall,result)
If (success = False) Then
    //  Examine the result for an exception.
    System.DebugLog(result.Emit())

    //  Also examine the LastErrorText.
    System.DebugLog(js.LastErrorText)
    Return
End If

System.DebugLog(result.Emit())

//  Output:

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

Dim retval As Int32
retval = result.IntOf("value")
System.DebugLog("retval = " + Str(retval))

JavaScript

function calculateScore(name, pointsA, pointsB) {
    // Return length of name + both scores
    return name.length + pointsA + pointsB;
    }