Javascript Module Pattern Isolation

Question

I'm trying to create some isolation in javascript using the module pattern.

but when i run this code:

var mymap = {};

mymap['230'] = (function () {
    privatePageLoad = function(nid, page){
        console.log('PAGE LOAD from 230: '+nid);
    }

    function handleDocummentAdded() {
        console.log("New Document in 230!");
        privatePageLoad(230, 0);
    };

    return {
        newDocument: handleDocummentAdded
    }
})();

mymap['318'] = (function () {
    privatePageLoad = function(nid, page){
        console.log('PAGE LOAD from 318: '+nid);
    }

    function handleDocummentAdded() {
        console.log("New Document in 318!");
        privatePageLoad(318, 0);
    };

    return {
        newDocument: handleDocummentAdded
    }
})();

mymap['230'].newDocument();
mymap['318'].newDocument();

I get the following result:

New Document in 230! (index):29
PAGE LOAD from 318: 230 (index):40
New Document in 318! (index):44
PAGE LOAD from 318: 318

but i was expecting:

New Document in 230! (index):29
PAGE LOAD from 230: 230 (index):40
New Document in 318! (index):44
PAGE LOAD from 318: 318

The private method that is called is always the last added to the map... What did i do wrong?

Here is a jsfiddle with it http://jsfiddle.net/jpedro/4xdTA/

Minko Gechev · Accepted Answer · 2014-02-20 17:47:37Z

privatePageLoad is not private at all. Add var , otherwise privatePageLoad will be global (i.e. property of the global object (window, module, whatever))

Change your code to something like:

var mymap = {};

mymap['230'] = (function () {
    var privatePageLoad = function(nid, page){
        console.log('PAGE LOAD from 230: '+nid);
    }

    function handleDocummentAdded() {
        console.log("New Document in 230!");
        privatePageLoad(230, 0);
    };

    return {
        newDocument: handleDocummentAdded
    }
})();

mymap['318'] = (function () {
    var privatePageLoad = function(nid, page){
        console.log('PAGE LOAD from 318: '+nid);
    }

    function handleDocummentAdded() {
        console.log("New Document in 318!");
        privatePageLoad(318, 0);
    };

    return {
        newDocument: handleDocummentAdded
    }
})();

Pointy · Accepted Answer · 2014-02-20 17:47:16Z

2

You forgot to declare "privatePageLoad" with var. Thus, it's a global variable.

You could also use a function declaration statement:

mymap['230'] = (function () {
    function privatePageLoad(nid, page){
        console.log('PAGE LOAD from 230: '+nid);
    }

    function handleDocummentAdded() {
        console.log("New Document in 230!");
        privatePageLoad(230, 0);
    };

    return {
        newDocument: handleDocummentAdded
    }
})();

Also, get into the habit of putting

"use strict";

at the top of your code. That would have resulted in an error in this case.

answered Feb 20, 2014 at 17:47

Pointy

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