IE COM automation: How to get the return value of `window.execScript` in PowerShell

Question

From this other post it looks like it is possible to get the return value of IHTMLWindow2::execScript from Internet Explorer API, however the linked example is

Answer 1

The preferred method is probably what @Matt suggested to use the eval method instead of execScript which has been deprecated in IE11. However, I still couldn't find how to access that eval from IE API. I created this other question to follow up with that.

I could, however, figure a way to execute JavaScript/jQuery on a web page and return the results back to PowerShell with this trick that we store the JavaScript return value in the DOM using setAttribute and then retrieving it in PowerShell using getAttribute.

# some web page with jQuery in it
$url = "http://jquery.com/"

# Use this function to run JavaScript on a web page. Your $jsCommand can
# return a value which will be returned by this function unless $global
# switch is specified in which case $jsCommand will be executed in global
# scope and cannot return a value. If you received error 80020101 it means
# you need to fix your JavaScript code.
Function ExecJavaScript($ie, $jsCommand, [switch]$global)
{
    if (!$global) {
        $jsCommand = "document.body.setAttribute('PSResult', (function(){$jsCommand})());"
    }
    $document = $ie.document
    $window = $document.parentWindow
    $window.execScript($jsCommand, 'javascript') | Out-Null
    if (!$global) {
        return $document.body.getAttribute('PSResult')
    }
}

Function CheckJQueryExists
{
    $result = ExecJavaScript $ie 'return window.hasOwnProperty("$");'
    return ($result -eq $true)
}

$ie = New-Object -COM InternetExplorer.Application -Property @{
    Navigate = $url
    Visible = $false
}
do { Start-Sleep -m 100 } while ( $ie.ReadyState -ne 4 )

$jQueryExists = CheckJQueryExists $ie
echo "jQuery exists? $jQueryExists"

# make a jQuery call
ExecJavaScript $ie @'
    // this is JS code, remember to use semicolons
    var content = $('#home-content');
    return content.text();
'@

# Quit and dispose IE COM
$ie.Quit()
[System.Runtime.Interopservices.Marshal]::ReleaseComObject($ie) | out-null
Remove-Variable ie