Xojo Plugin

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. Xojo Plugin

Dim success As Boolean
success = False

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

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

Dim sbScript As New Chilkat.StringBuilder
success = sbScript.Append("function describeCar(car) { console.log(`This is a ${car.year} ${car.make} ${car.model}.`); }")

Dim js As New Chilkat.Js

Dim result As New Chilkat.JsonObject
result.EmitCompact = False

// Call Eval to add the function 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

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

Dim funcCall As New Chilkat.JsonObject
funcCall.EmitCompact = False

// 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
//     }
//   ]
// }

success = funcCall.UpdateString("name","describeCar")

// Create the JSON object that is the argument.
Dim arg As New Chilkat.JsonObject
success = arg.UpdateString("make","Toyota")
success = arg.UpdateString("model","Corolla")
success = arg.UpdateInt("year",2022)

// Create the arguments array.
Dim argsArray As New Chilkat.JsonArray
success = argsArray.AddObjectCopyAt(0,arg)

// Add the "args" array to the funcCall.
success = funcCall.AppendArrayCopy("args",argsArray)

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())

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

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

// However, the function emitted text to the console.

Dim sbOut As New Chilkat.StringBuilder
js.ConsoleOutputSb sbOut
System.DebugLog(sbOut.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:

funcCall.Clear 
success = funcCall.UpdateString("name","describeCar")
success = funcCall.UpdateString("args[0].make","Toyota")
success = funcCall.UpdateString("args[0].model","Corolla")
success = funcCall.UpdateInt("args[0].year",2022)
System.DebugLog(funcCall.Emit())