VB.NET Requires Chilkat v11.4.0+

Call a JavaScript Function Returning a Boolean

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Demonstrates how to call a JavaScript function that returns a boolean. VB.NET

Dim success As Boolean = False

'  This is the JavaScript function we'll call:

'  function isEven(number) {
'      return number % 2 === 0;
'  }

Dim sbScript As New Chilkat.StringBuilder
sbScript.Append("function isEven(number) { return number % 2 === 0; }")

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 isEven(8)

Dim funcCall As New Chilkat.JsonObject

'  Create JSON specifying the function name and arguments

'  {
'    "name": "isEven",
'    "args": [ 8 ]
'  }

funcCall.UpdateString("name","isEven")
funcCall.UpdateInt("args[0]",8)

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())

'  Output:
'  {
'    "type": "bool",
'    "value": true
'  }

Dim retval As Boolean = result.BoolOf("value")
Debug.WriteLine(retval)

'  Output:
'  True