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())

JavaScript

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;
}