how to push data into array in another array

[Dallok97]

db.defaults({
device : [],
area : [{init : [], enter :[], work :[], quit :[]}],
vehicle :[{init : [], enter :[], work :[], quit :[]}]
}).write()

scandata = {
macaddress : "",
uuid: ""
}

how to push the scandata at 'init' in 'area'