Lianja

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. Lianja

llSuccess = .F.

// This is the JavaScript function we'll call:

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

loSbScript = createobject("CkStringBuilder")
loSbScript.Append("function describeCar(car) { console.log(`This is a ${car.year} ${car.make} ${car.model}.`); }")

loJs = createobject("CkJs")

loResult = createobject("CkJsonObject")
loResult.EmitCompact = .F.

// Call Eval to add the function to the context's global object
llSuccess = loJs.Eval(loSbScript,loResult)
if (llSuccess = .F.) then
    // Examine the result for an exception.
    ? loResult.Emit()

    // Also examine the LastErrorText.
    ? loJs.LastErrorText
    release loSbScript
    release loJs
    release loResult
    return
endif

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

loFuncCall = createobject("CkJsonObject")
loFuncCall.EmitCompact = .F.

// 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("CkJsonObject")
loArg.UpdateString("make","Toyota")
loArg.UpdateString("model","Corolla")
loArg.UpdateInt("year",2022)

// Create the arguments array.
loArgsArray = createobject("CkJsonArray")
loArgsArray.AddObjectCopyAt(0,loArg)

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

? loFuncCall.Emit()

llSuccess = loJs.CallFunction(loFuncCall,loResult)
if (llSuccess = .F.) 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
    return
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("CkStringBuilder")
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