Visual FoxPro

Call a JavaScript Function Returning an Integer

See more JavaScript Examples

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

LOCAL lnSuccess
LOCAL loSbScript
LOCAL loJs
LOCAL loResult
LOCAL loFuncCall
LOCAL lnRetval

lnSuccess = 0

*  ----------------------------------------------------------------------------------
*  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.
loSbScript = CreateObject('Chilkat.StringBuilder')
lnSuccess = loSbScript.LoadFile("js_call_function.js","utf-8")
IF (lnSuccess = 0) THEN
    ? loSbScript.LastErrorText
    RELEASE loSbScript
    CANCEL
ENDIF

*  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.
loJs = CreateObject('Chilkat.Js')

loResult = CreateObject('Chilkat.JsonObject')
loResult.EmitCompact = 0

*  Call Eval to add the function (shown at the bottom of this page) to the context's global object
lnSuccess = loJs.Eval(loSbScript,loResult)
IF (lnSuccess = 0) THEN
    *  Examine the result for an exception.
    ? loResult.Emit()

    *  Also examine the LastErrorText.
    ? loJs.LastErrorText
    RELEASE loSbScript
    RELEASE loJs
    RELEASE loResult
    CANCEL
ENDIF

? loResult.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)

loFuncCall = CreateObject('Chilkat.JsonObject')

*  Create JSON defining the function call:

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

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

loFuncCall.EmitCompact = 0
? loFuncCall.Emit()

lnSuccess = loJs.CallFunction(loFuncCall,loResult)
IF (lnSuccess = 0) THEN
    *  Examine the result for an exception.
    ? loResult.Emit()

    *  Also examine the LastErrorText.
    ? loJs.LastErrorText
    RELEASE loSbScript
    RELEASE loJs
    RELEASE loResult
    RELEASE loFuncCall
    CANCEL
ENDIF

? loResult.Emit()

*  Output:

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

lnRetval = loResult.IntOf("value")
? "retval = " + STR(lnRetval)

RELEASE loSbScript
RELEASE loJs
RELEASE loResult
RELEASE loFuncCall

JavaScript

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