Is There a JSON Parser for VB6 / VBA?

Building on ozmike solution, which did not work for me (Excel 2013 and IE10). The reason is that I could not call the methods on the exposed JSON object. So its methods are now exposed through functions attached to a DOMElement. Didn't know this is possible (must be that IDispatch-thing), thank you ozmike.

As ozmike stated, no 3rd-party libs, just 30 lines of code.

Option Explicit

Public JSON As Object
Private ie As Object

Public Sub initJson()
    Dim html As String

    html = "<!DOCTYPE html><head><script>" & _
    "Object.prototype.getItem=function( key ) { return this[key] }; " & _
    "Object.prototype.setItem=function( key, value ) { this[key]=value }; " & _
    "Object.prototype.getKeys=function( dummy ) { keys=[]; for (var key in this) if (typeof(this[key]) !== 'function') keys.push(key); return keys; }; " & _
    "window.onload = function() { " & _
    "document.body.parse = function(json) { return JSON.parse(json); }; " & _
    "document.body.stringify = function(obj, space) { return JSON.stringify(obj, null, space); }" & _
    "}" & _
    "</script></head><html><body id='JSONElem'></body></html>"

    Set ie = CreateObject("InternetExplorer.Application")
    With ie
        .navigate "about:blank"
        Do While .Busy: DoEvents: Loop
        Do While .readyState <> 4: DoEvents: Loop
        .Visible = False
        .document.Write html
        .document.Close
    End With

    ' This is the body element, we call it JSON:)
    Set JSON = ie.document.getElementById("JSONElem")

End Sub

Public Function closeJSON()
    ie.Quit
End Function

The following test constructs a JavaScript Object from scratch, then stringifies it. Then it parses the object back and iterates over its keys.

Sub testJson()
    Call initJson

    Dim jsObj As Object
    Dim jsArray As Object

    Debug.Print "Construction JS object ..."
    Set jsObj = JSON.Parse("{}")
    Call jsObj.setItem("a", 1)
    Set jsArray = JSON.Parse("[]")
    Call jsArray.setItem(0, 13)
    Call jsArray.setItem(1, Math.Sqr(2))
    Call jsArray.setItem(2, 15)
    Call jsObj.setItem("b", jsArray)

    Debug.Print "Object: " & JSON.stringify(jsObj, 4)

    Debug.Print "Parsing JS object ..."
    Set jsObj = JSON.Parse("{""a"":1,""b"":[13,1.4142135623730951,15]}")

    Debug.Print "a: " & jsObj.getItem("a")
    Set jsArray = jsObj.getItem("b")
    Debug.Print "Length of b: " & jsArray.getItem("length")
    Debug.Print "Second element of b: "; jsArray.getItem(1)

    Debug.Print "Iterate over all keys ..."
    Dim keys As Object
    Set keys = jsObj.getKeys("all")

    Dim i As Integer
    For i = 0 To keys.getItem("length") - 1
        Debug.Print keys.getItem(i) & ": " & jsObj.getItem(keys.getItem(i))
    Next i

    Call closeJSON
End Sub

outputs

Construction JS object ...
Object: {
    "a": 1,
    "b": [
        13,
        1.4142135623730951,
        15
    ]
}
Parsing JS object ...
a: 1
Length of b: 3
Second element of b:  1,4142135623731 
Iterate over all keys ...
a: 1
b: 13,1.4142135623730951,15

Check out JSON.org for an up-to-date list (see bottom of main page) of JSON parsers in many different languages. As of the time of this writing, you'll see a link to several different JSON parsers there, but only one is for VB6/VBA (the others are .NET):

VB-JSON
- When I tried to download the zip file, Windows said the data was corrupt. However, I was able to use 7-zip to pull the files out. It turns out that the main "folder" in the zip file isn't recognized as a folder by Windows, by 7-zip can see the contents of that main "folder," so you can open that up and then extract the files accordingly.
- The actual syntax for this VB JSON library is really simple:
```
Dim p As Object
Set p = JSON.parse(strFormattedJSON)

'Print the text of a nested property '
Debug.Print p.Item("AddressClassification").Item("Description")

'Print the text of a property within an array '
Debug.Print p.Item("Candidates")(4).Item("ZipCode")
```
- Note: I had to add the "Microsoft Scripting Runtime" and "Microsoft ActiveX Data Objects 2.8" library as references via Tools > References in the VBA editor.
- Note: VBJSON code is actually based on a google code project vba-json. However, VBJSON promises several bug fixes from the original version.

Is There a JSON Parser for VB6 / VBA?

Tags:

Web Services

Vb6

Vba

Serialization

Json

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