getElementsByClassName not working in VBS

Question

I have a VBS script in an HTA that is supposed to verify the login credentials from an HTA login form by attempting to login at an external webpage with the same credentials. "getElementsByClassName" doesn't seem to work though, cause each time I run the script it outputs:

Object doesn't support this property or method: 'IE.Document.getElementsByClassName(...).innerHTML'

This script is supposed to open a login page in IE, input login credentials and test for an error message. The error message appears on the page if the credentials are wrong, and has the class "alert alert-error".

<script language="vbscript">

Set IE = CreateObject("InternetExplorer.application")
IE.Visible = True
IE.navigate "https://www.mypage.com/login"

Do Until IE.ReadyState = 4
wscript.sleep 200
Loop

IE.Document.All.Item("username").Value = "loginUsername"
IE.Document.All.Item("password").Value = "loginPassword"
IE.Document.All.Item("submit").Click

Do Until IE.ReadyState = 4
wscript.sleep 200
Loop

set error = IE.Document.getElementsByClassName("alert alert-error").innerHTML
if error="" then
X=MsgBox("You have successfully been logged in!")
else
X=MsgBox("An error occured, you are not logged in.")
end if

</script>

I hope this is enough information to solve the problem. Thank you!

Answer 1

First and foremost, getElementsByClassName() returns a collection of element objects of the specified className, it's not a single object. So the statement getElementsByClassName("alert alert-error").innerHTML is invalid and will generate an error.

You will have to enumerate the collection to target objects inside it in a manner similar to the following:

var colAlertErrorElements = IE.Document.getElementsByClassName("alert alert-error");

for (var i=0; i<colAlertErrorElements.length; i++) {
    var objErrorElement = colAlertErrorElements[i];
    if (objErrorElement.innerHTML == "') {
        // no error
    }
    else {
        // error
    }
}

Answer 2

You have to write your own fnc, it does not come embed in the DOM object. I basically translate an old JavaScript fnc written years ago for admin-management via the web. The DOM provide the same functionality regarless of the language queryring it (js, vbs, etc).

I include a 'GetParentTagName' fnc to skip the search from the body document (faster). Refer to 'GetElementsByClass' fnc for the core script. You can ajust for having a more generic i.e. search any attribute name, not just a class attribute.

Here is the code (HTML ex + VBS for HTA) :

HTML code
=========
<table name="product_not_approve">
    <tbody name="cieA" >
        <tr class="tr_205F51AF-4245-4258-96A3-76DC13B978BB">
            <td fieldname="checkbox_delete">
                <input type="checkbox" name="delete_opt_cieA" value="205F51AF-4245-4258-96A3-76DC13B978BB" />
            </td>
        </tr>
    </tbody>
    <tfoot>
        <tr>
            <td>
                <a href="#" onclick="Admin_Accept_Save_Change me">Make change</a>
            </td>
        </tr>
    </tfoot>
</table>

VBS code
' =================================================================
Sub Admin_Accept_Save_Change(this)

    'msgbox this = window.event.srcElement
    'msgbox this.outerHTML

    Dim oEleParent : Set oEleParent = GetParentTagName(this, "table")
    'msgbox oEleParent.tagName & " - " & oEleParent.outerHTML

    ' Fnc GetElementsByClass((searchClass, node, tag)) return a dictionary object, node can be null, search from DOM body
    Dim oEles : Set oEles = GetElementsByClass("tr_" & "205F51AF-4245-4258-96A3-76DC13B978BB", oEleParent, "tr")
    Dim oEle

    For i = 0 To oEles.Count - 1
        'msgbox oEles.Keys()(i) & ", " & TypeName(oEles.Items()(i))
        Set oEle = oEles.Items()(i)
        msgbox oEle.outerHTML
    Next

    ' Cancel href event
    window.event.returnValue = False

End Sub


' =================================================================
Function GetParentTagName(oEle, tagName)

    Dim oParent : Set oParent = oEle.parentNode ' oEle.parentElement.outerHTML

    Do While UCase(oParent.tagName) <> UCase(tagName)
        Set oParent = oParent.parentNode

        If UCase(oParent.tagName) = "BODY" Then
            Set oParent = Nothing
            Exit Do
        End If
    Loop  

    Set GetParentTagName = oParent

End Function


' =================================================================
Function GetElementsByClass(searchClass, node, tag)

    If IsNull(node) Then Set node = document
    If IsNull(tag) Or tag = "" Then tag = "*"

    Dim oElements : Set oElements = node.getElementsByTagName(tag)
    Dim oDic : Set oDic = CreateObject("Scripting.Dictionary")
    oDic.CompareMode = vbTextCompare

    ' msgbox "typename node = " & TypeName(node) & vbCrLf & _
           ' "tag = " & tag & vbCrLf & _
           ' "searchClass = " & searchClass & vbCrLf & _
           ' "nb of ele found = " & oElements.length

    Dim i : i = 0
    Dim oEle, oAtt

    Do While i < oElements.length
        Set oEle = oElements(i)
        Set oAtt = oEle.Attributes.getNamedItem("class") ' Return a DispHTMLDOMAttribute object

        If oAtt.value = searchClass Then
            'msgbox "Found class : " & oAtt.name & " - " & oAtt.value
            oDic.Add oDic.count + 1, oEle
        End If

        i = i + 1
    Loop

    'msgbox "Nb of DOM element found : " & oDic.Count
    Set GetElementsByClass = oDic

End Function