Call external declared variable inside the function

Question

I wrote a function to check if there is a data saved in "phonenumber" child on my firebase database or not .. the tests are OKEY! but inside this function I can't call an external declared variable ! this is code:

phoneNumberExistence: boolean;

FIREBASE_DATABASE.ref("Settings").child('phoneNumber').once('value', function(snapshot) {
      var exists = (snapshot.val() !== null);
      //console.log("Phone number existance: "+exists);
      if(exists){
        this.phoneNumberExistence = true; //the problem is here.. can't use this variable
        console.log("A phone number already exists.")
      }
      else{
        this.phoneNumberExistence = false; //the problem is here.. can't use this variable
        console.log("There is no phone number here :(");
      }
    })

Any idea ? thanks

Personally, I ***never*** use `this` in Angular. Stick with `$scope`. See https://stackoverflow.com/questions/11605917/this-vs-scope-in-angularjs-controllers — Mawg says reinstate Monica, Aug 30 '18 at 11:45

score 0 · Accepted Answer · answered Aug 30 '18 at 11:49

0

Use arrow functions instead of function(snapshot) {...}

... .once('value', (snapshot) => {
  var exists = (snapshot.val() !== null);
  ...
});

Arrow Functions lexically bind their context so this actually refers to the originating context. For more details, you can read this article.

answered Aug 30 '18 at 11:49

shohrukh

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I didn't knew that type of functions, anyway your solution worked perfectly, thanks man – Arselan Aug 30 '18 at 12:00
U r welcome. This an EcmaScript 6 feature, so you can also use it in TypeScript. – shohrukh Aug 30 '18 at 12:01

Call external declared variable inside the function

1 Answers1