Array.prototype.find() returns undefined in async function

Question

I have an issue with the Array.prototype.find() method. It doesn't seem to work properly when it is used in $http request.. I've tried everything that came to mind but it always returns undefined. I guess the bug is there because I logged response.data and user_to_find before defining found_user and their values are as expected.

So I have this service:

app.service('UserService', ['$http','$q', function($http, $q) {
  return {
    findUser: function(user_to_find) {
      let defer = $q.defer();
      $http({
        method: "GET",
        url: 'http://localhost:3000/users'
      }).then(function(response){
        let found_user = response.data.find(acc=>{ //found_user is always undefined
          acc.username == user_to_find;
        })
        defer.resolve(found_user);
      }),function(response) {
        defer.reject(response);
        console.log("Error finding user");
      }
      return defer.promise;
    }
  }
}])

Solution

Your are missing a return. The predicate (the function passed to find) returns undefined in your case, so the find algorithm does not get a "match".

Just add the return:

    let found_user = response.data.find(acc=>{ //found_user is always undefined
      return acc.username == user_to_find;
    })

You can leave it out, if you are not using curly braces

    let found_user = response.data.find(acc=> ( //found_user is always undefined
      acc.username === user_to_find;
    ))

I'd recommend also to use === (strict comparison) instead of == for comparison.

Comments

[Admin]

Oh my god. I feel so stupid, I thought that my mistake is in the promises.. I've been looking for it a whole day.. Thank you so much and sorry for the dumb question! I will follow your advice for the strict comparison, thank you!

[lipp]

You are welcome! Don't worry, everybody did have similar issues more than once :)