Visual FoxPro

Call a JavaScript Function Passing an Object Argument

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Demonstrates how to call a JavaScript function with an argument that is an object. Visual FoxPro

LOCAL lnSuccess
LOCAL loSbScript
LOCAL loJs
LOCAL loResult
LOCAL loFuncCall
LOCAL loArg
LOCAL loArgsArray
LOCAL loSbOut

lnSuccess = 0

* This is the JavaScript function we'll call:

* function describeCar(car) {
* 	console.log(`This is a ${car.year} ${car.make} ${car.model}.`);
* }

loSbScript = CreateObject('Chilkat.StringBuilder')
loSbScript.Append("function describeCar(car) { console.log(`This is a ${car.year} ${car.make} ${car.model}.`); }")

loJs = CreateObject('Chilkat.Js')

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

* Call Eval to add the function 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

* ------------------------------------------------------------------------------
* Call the function describeCar(car)

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

* Create JSON specifying the function name and arguments
* In this case, there is only 1 argument, and it is an object.

* {
*   "name": "describeCar",
*   "args": [
*     {
*       "make": "Toyota",
*       "model": "Corolla",
*       "year": 2022
*     }
*   ]
* }

loFuncCall.UpdateString("name","describeCar")

* Create the JSON object that is the argument.
loArg = CreateObject('Chilkat.JsonObject')
loArg.UpdateString("make","Toyota")
loArg.UpdateString("model","Corolla")
loArg.UpdateInt("year",2022)

* Create the arguments array.
loArgsArray = CreateObject('Chilkat.JsonArray')
loArgsArray.AddObjectCopyAt(0,loArg)

* Add the "args" array to the funcCall.
loFuncCall.AppendArrayCopy("args",loArgsArray)

? 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
    RELEASE loArg
    RELEASE loArgsArray
    CANCEL
ENDIF

? loResult.Emit()

* The describeCar JavaScript function returns nothing. 
* Therefore, the result is "undefined".

* {
*   "type": "undefined",
*   "value": "undefined"
* }

* However, the function emitted text to the console.

loSbOut = CreateObject('Chilkat.StringBuilder')
loJs.ConsoleOutputSb(loSbOut)
? loSbOut.GetAsString()

* Output:
* This is a 2022 Toyota Corolla.

* -----------------------------------------------------------
* Note: If the object argument is simple, this is an alternative
* and simpler way of creating the funcCall:

loFuncCall.Clear()
loFuncCall.UpdateString("name","describeCar")
loFuncCall.UpdateString("args[0].make","Toyota")
loFuncCall.UpdateString("args[0].model","Corolla")
loFuncCall.UpdateInt("args[0].year",2022)
? loFuncCall.Emit()

RELEASE loSbScript
RELEASE loJs
RELEASE loResult
RELEASE loFuncCall
RELEASE loArg
RELEASE loArgsArray
RELEASE loSbOut