Call "private" method from "parent" object in javascript

Question

in the following code, i need call the "private" method run in the sub class Worker

function Person(scope, ...) {
  scope.name = "Juan";

  var run = function() {
     console.log(scope.name + " is running");
  };
}

function Worker(scope, ...) {
  Person.call(this, scope, ...);

  var jumpAndRun = function() {
     console.log(scope.name + " is jumping");
     run(); // how to call this
  };
}

Worker.prototype = Object.create(People.prototype);

currently if i call run method i get an Error: run is not defined!

That's outright impossible. It's totally private to the People constructor function scope, not somehow "protected". — Bergi
– Bergi, Commented Sep 9, 2014 at 15:05
Why can't you make it public? From where are run and jumpAndRun invoked anyway? — Bergi
– Bergi, Commented Sep 9, 2014 at 15:06
My recommendation: Don't try to simulate something that the language does not support. Keep it simple. It makes the code: easier to understand and easier to maintain. — Felix Kling
– Felix Kling, Commented Sep 9, 2014 at 15:07
@FelixKling yeah you are right but i wont rewrite many code is the same in many places, currently i'm refactoring — rkmax
– rkmax, Commented Sep 9, 2014 at 15:16

rkmax · Accepted Answer · 2014-09-09 15:38:09Z

3

Sorry, can't do it, unless the People class (which should be called Person) makes that method available.

A common practice is to make "private" methods start with an underscore. It does not 100% grant any security, but it at least gives other developers a hint that it is meant to be private.

function Person(scope, ...) {
  scope.name = "Juan";

  var run = function() {
     console.log(scope.name + " is running");
  };

  this._run = run;
}

function Worker(scope, ...) {
  Person.call(this, scope, ...);

  var jumpAndRun = function() {
     console.log(scope.name + " is jumping");
     this._run(); // how to call this
  };
}

edited Sep 9, 2014 at 15:38

rkmax

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answered Sep 9, 2014 at 15:06

000

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3 Comments

Bergi Over a year ago

Your jumpAndRun function would need to be a method as well, though.

Simone Gianni Over a year ago

@rkmax have you added the this._run = run; in the Person costructor?

000 Over a year ago

Here I've done what I think is right, here is a fiddle: jsfiddle.net/zLqb1tyo

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