VB.NET Requires Chilkat v11.4.0+

Call a JavaScript Function Returning a String

See more JavaScript Examples

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

Dim success As Boolean = False

'  This is the JavaScript function we'll call:

'  function greet(name) {
'      return "Hello, " + name + "!";
'  }

Dim sbScript As New Chilkat.StringBuilder
sbScript.Append("function greet(name) { return ""Hello, "" + name + ""!""; }")

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 greet("Michael")

Dim funcCall As New Chilkat.JsonObject

'  Create JSON specifying the function name and arguments

'  {
'    "name": "greet",
'    "args": [ "Michael" ]
'  }

funcCall.UpdateString("name","greet")
funcCall.UpdateString("args[0]","Michael")

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": "string",
'    "value": "Hello, Michael!"
'  }

Dim retval As String = result.StringOf("value")
Debug.WriteLine(retval)

'  Output:
'  Hello, Michael!