VB.NET

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