How to make an a check to undefined

Question

I have got a project, where need to make a check to undifined. How can i do it, because, if i try:

  var sorted_arr = arrayOfParasites.sort((b, a) => a[1] - b[1]);
  console.log(sorted_arr)

It takes an exception:

TypeError: Cannot read property 'sort' of undefined

Only you know where `arrayOfParasites` is defined and assigned a value. — Phil, Dec 23 '22 at 07:09
You've got an exception because value of arrayOfParasites is undefined — Tatul Mkrtchyan, Dec 23 '22 at 07:10

score 1 · Answer 1 · answered Dec 23 '22 at 07:09

the optional chaining operator in JS. By adding the ? before the method, it will return undefined instead of throwing an error if that method doesn't exist for that variable/type

var arrayOfParasites = undefined;
var sorted_arr = arrayOfParasites?.sort((b, a) => a[1] - b[1]);
  console.log(sorted_arr)

How to make an a check to undefined

1 Answers1