VB.NET

Call a JavaScript Function Passing an Array Argument

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Demonstrates how to call a JavaScript function with an argument that is an array. VB.NET

Dim success As Boolean = False

' This is the JavaScript function we'll call:

' function calculateTotal(numbers) {
'   console.log(numbers);
'   let total = 0;
'   
'   // Loop through every number in the array
'   for (const num of numbers) {
'     console.log(num);
'     total += num;
'   }
'   
'   return total;
' }

Dim sbScript As New Chilkat.StringBuilder
success = sbScript.LoadFile("js_function_array_arg.js","utf-8")
If (success = False) Then
    Debug.WriteLine(sbScript.LastErrorText)
    Exit Sub
End If


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.
    Debug.WriteLine(result.Emit())

    ' Also examine the LastErrorText.
    Debug.WriteLine(js.LastErrorText)
    Exit Sub
End If


' ------------------------------------------------------------------------------
' Call the function calculateTotal(numbers)

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 array.

funcCall.UpdateString("name","calculateTotal")

' Create the arguments array.
Dim argsArray As New Chilkat.JsonArray

' The 1st argument in the arguments array is itself an array.
' Passing -1 indicates to append to the array.
Dim arg As New Chilkat.JsonArray
argsArray.AddArrayAt2(-1,arg)

' Fill in the values for the 1st argument.
arg.AddNumberAt(-1,"10.50")
arg.AddNumberAt(-1,"20.00")
arg.AddNumberAt(-1,"5.25")

' Add the "args" array to the funcCall.
funcCall.AppendArrayCopy("args",argsArray)

Debug.WriteLine(funcCall.Emit())

' The funcCall is as follows.  Notice that the 1st (and only) argument is an array.

' {
'   "name": "calculateTotal",
'   "args": [
'     [
'       10.50,
'       20.00,
'       5.25
'     ]
'   ]
' }

success = js.CallFunction(funcCall,result)
If (success = False) Then
    ' Examine the result for an exception.
    Debug.WriteLine(result.Emit())

    ' Also examine the LastErrorText.
    Debug.WriteLine(js.LastErrorText)
    Exit Sub
End If


Debug.WriteLine(result.Emit())

' Result:
' {
'   "type": "double",
'   "value": 35.75
' }

' The function also emitted text to the console.

Dim sbOut As New Chilkat.StringBuilder
js.ConsoleOutputSb(sbOut)
Debug.WriteLine(sbOut.GetAsString())

' Output:
' 10.5,20,5.25
' 10.5
' 20
' 5.25

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

funcCall.Clear()
funcCall.UpdateString("name","calculateTotal")
funcCall.UpdateNumber("args[0][0]","10.50")
funcCall.UpdateNumber("args[0][1]","20.00")
funcCall.UpdateNumber("args[0][2]","5.25")
Debug.WriteLine(funcCall.Emit())