Function returned undefined, expected Promise or value

Question

Whern i fire Simple database trigger on firebase, then it will shows Error like this : \"Function returned undefined, expected Promise or value\"

Answer 1

If you just want the error to disappear you could simply just

return new Promise((resolve, reject) => {
    resolve("A Notification has been deleted from the database ")
})

but it would be kinda pointless to return a string here.

If it's just for testing you could

console.log("A Notification has been deleted from the database ")

instead.