So, many questions on the StackOverflow VBA thread are concerned with web-scraping and so driving the browser in VBA code is a useful skill. Here we're see that we can push the boundary a little more by firing events in the HTML object model.
Code To Write HTML
Here we write some code to write the html file locally. The code uses the HtmlElementStack class (given separately below) to ensure our HTML is well-formed. There is a script tag which defines the function wired to the button's click handler. But we shall see that because the function is defined in the HTML page's global scope, i.e. Window object, then it can be called with Window.execScript
Private Const msFILENAME As String = "N:\TestJavascript2.html"
Function WriteHTML()
Dim dicHTMLStack As HtmlElementStack
Set dicHTMLStack = New HtmlElementStack
With dicHTMLStack
.SetFileName msFILENAME
.OE "html"
.OE "head"
.OE "title"
.WL "Some test html with javascript"
.CE
.CE
.OE "body"
.OE "div", "id='div1'"
.WL "Some Text"
.CE
.OE "button", "id='button1' type='button' onclick='throwMsgBox()'"
.WL "Click Me!"
.CE
.OE "script", "language='jscript'"
.WL "function throwMsgBox() { alert('hi there'); }"
.CE
End With
Set dicHTMLStack = Nothing
End Function
HtmlElementStack class
This class allows us to be a little lazy when writing html files. We keep a stack, ie. Last In Last Out (LIFO) structure in a Scripting.Dictionary, that records all the open elements that need closing. It also manages its own text stream because we need to write off all pending close elements before the text stream is closed.
Option Explicit
'* Tools->References
' Scripting Microsoft Scripting Runtime C:\Windows\SysWOW64\scrrun.dll
Private mdicStack As New Scripting.Dictionary
Private mtxt As Scripting.TextStream
Private msFILENAME As String
Private mfso As New Scripting.FileSystemObject
'Private Sub SetStream(ByVal txt As Scripting.TextStream)
' Set mtxt = txt
'End Sub
Public Sub SetFileName(ByVal sFileName As String)
msFILENAME = sFileName
Set mtxt = mfso.CreateTextFile(msFILENAME)
End Sub
Public Sub Write_(ByVal sText As String)
mtxt.Write sText
End Sub
Public Sub WL(ByVal sText As String)
mtxt.WriteLine sText
End Sub
Public Sub OE(ByVal sNodeName As String, Optional ByVal sAttribs As String)
If Not mtxt Is Nothing Then
If Len(sAttribs) = 0 Then
mtxt.WriteLine "<" & sNodeName & ">"
Else
mtxt.WriteLine "<" & sNodeName & " " & sAttribs & ">"
End If
End If
mdicStack.Add mdicStack.Count, sNodeName
End Sub
Public Sub CE()
If mdicStack.Count > 0 Then
Dim sLastNode As String
sLastNode = mdicStack.Item(mdicStack.Count - 1)
Call mdicStack.Remove(mdicStack.Count - 1)
mtxt.WriteLine ""
End If
End Sub
Private Sub Class_Terminate()
While mdicStack.Count > 0
DoEvents
CE
DoEvents
Wend
mtxt.Close
Set mtxt = Nothing
End Sub
Code to drive IE and call the click handler function 3 different ways
So in this code we create an instance of IE and navigate to our newly written html file. We call the button's click handler function 3 different ways. Firstly, by navigating to element and call 'Click'. Secondly, by calling the function in the global scope (i.e. off the window object) using ExecScript. Thirdly, similar to first but a looser couple FireEvent method.
I recommend acquiring the element immediately before calling a method because I have witnessed a type of stale reference bug.
Private Const msFILENAME As String = "N:\TestJavascript2.html"
Public Sub TestFire()
'* Tools->References
'SHDocVw Microsoft Internet Controls C:\Windows\SysWOW64\ieframe.dll
Dim oIE As InternetExplorerMedium
Set oIE = New InternetExplorerMedium
oIE.Visible = True
oIE.navigate msFILENAME
While oIE.Busy Or oIE.readyState < 4
DoEvents
Wend
Stop
'* recommend re-acquiring element before using as I suspect IE suffers from stale references
oIE.Document.getElementById("button1").Click
Stop
'* call the function via the global scope, for html global scope is the *window*
Call oIE.Document.parentWindow.execScript("throwMsgBox()", "JavaScript")
Stop
'* recommend re-acquiring element before using as I suspect IE suffers from stale references
oIE.Document.getElementById("button1").FireEvent "onclick"
Stop
oIE.Quit
End Sub
