# wx.onShow(function callback)
Listens on the event that the Mini Game is switched to the foreground.
# function callback
The callback function for the event that the Mini Game is switched to the foreground.
# Object res
|referrerInfo||object||This field is returned when the Mini Game is opened from another Mini Program, Official Account, or app.|
referrerInfo is composed as follows
|appId||string||The appId of the source Mini Program, Official Account, or app.|
|extraData||object||The data transfered from the source Mini Program, supported when scene=1037 or 1038.|