The attached test project shows the difference between a QML var property used as a Javascript array:

property var qmlList: []

and a QVariantList used as a Javascript array:

Q_PROPERTY(QVariantList list READ list WRITE setList NOTIFY listChanged)

The QML declared list works as expected as a JS array. However, the C++ QVariantList accepts JS array operations (such as push, splice, etc) yet they have no effect.

I feel this may be related to #QTBUG-28602.

I noticed that QList properties works with int, bool, etc, so I added support for QVariantList in qv8sequencewrapper. I would have linked to a patch on gerrit, but I was having trouble pushing it successfully. For now, I've attached the patch, I'll have another look at gerrit stuff tomorrow.