How to check the existence of an object?

Question

Node.js

Hello, how can I check for the existence of an object ??
I tried this code, it does not check for the existence of
if(Lister==undefined)

Answer 1

if(typeof Lister === 'undefined') {
  // не существует
} else {
  // cуществует
}

if only the "exists" case is needed, then:

if(typeof Lister !== 'undefined') {
  // существует
}