Question

To make a JavaScript class with a public method I’d do something like:

function Restaurant() {}  Restaurant.prototype.buy_food = function(){    // something here }  Restaurant.prototype.use_restroom = function(){    // something here } 

That way users of my class can:

var restaurant = new Restaurant(); restaurant.buy_food(); restaurant.use_restroom(); 

How do I create a private method that can be called by the buy_food and use_restroom methods but not externally by users of the class?

In other words, I want my method implementation to be able to do:

Restaurant.prototype.use_restroom = function() {    this.private_stuff(); } 

But this shouldn’t work:

var r = new Restaurant(); r.private_stuff(); 

How do I define private_stuff as a private method so both of these hold true?

I’ve read Doug Crockford’s writeup a few times but it doesn’t seem like ‘private’ methods can be called by public methods and ‘privileged’ methods can be called externally.

Answer 1

You can do it, but the downside is that it can’t be part of the prototype:

function Restaurant() {     var myPrivateVar;      var private_stuff = function() {  // Only visible inside Restaurant()         myPrivateVar = 'I can set this here!';     }      this.use_restroom = function() {  // use_restroom is visible to all         private_stuff();     }      this.buy_food = function() {   // buy_food is visible to all         private_stuff();     } }