QWebEngineView runJavaScript() problem

[Pavlya]

Hello all.

I faced with some strange behavior in QWebEngineView.
I have a loaded page in QWebEngineView object witch has 'group0' element.
I run next script:

...
QString script = "document.getElementsByName('group0');";
page()->runJavaScript(script, [](const QVariant &v) {qDebug() << v;});
...

It prints

QVariant(QVariantMap, QMap())

But now I need value of first element of 'group0' (or array with several values). I tried to run script:

QString script = "var elems=document.getElementsByName('group0');" 
                 "system.log(elems[0].value);";
page()->runJavaScript(script, [](const QVariant &v) {qDebug() << v;});

But I got

QVariant(Invalid)

Documentation says

Runs the JavaScript code contained in scriptSource.

When the script has been executed, resultCallback is called with the result of the last executed statement.

Note: resultCallback can be any of a function pointer, a functor or a lambda, and it is expected to take a QVariant parameter.

Could you say me how can I return result of the last executed statement from script to callback.

Thank you.