up.Preview up.Preview.prototype.layer

Property

The layer that the previewed render pass is going to update.

When opening a new overlay, this property has the value "new":

up.preview('my-preview', function(preview) {
  if (preview.layer === 'new') {
    console.log("Opening a layer with mode", preview.renderOptions.mode)
  } else {
    console.log("Updating layer", preview.layer)
  }
})