JavaScript Patterns 5.1 Namespace Pattern

global namespace object

// global object

var MYAPP = {};

// constructors

MYAPP.Parent = function() {
};

MYAPP.Child = function() {
};

// a variable

MYAPP.some_var = 1;

// an object container

MYAPP.modules = {};

// nested objects

MYAPP.modules.module1 = {};

MYAPP.modules.module1.data = {
    a : 1,
    b : 2
};

MYAPP.modules.module2 = {};

Drawbacks

• A bit more to type; prefixing every variable and function does add up in the total amount of code that needs to be downloaded

• Only one global instance means that any part of the code can modify the global instance and the rest of the functionality gets the updated state

• Long nested names mean longer (slower) property resolution lookups

General Purpose Namespace Function

// unsafe

var MYAPP = {};

// better

if ( typeof MYAPP === "undefined") {

    var MYAPP = {};

}

// or shorter

var MYAPP = MYAPP || {};

// using a namespace function

MYAPP.namespace('MYAPP.modules.module2');

// equivalent to:

// var MYAPP = {

//      modules: {

//              module2: {}

//      }

// };

MYAPP.namespace = function(ns_string) {

    var parts = ns_string.split('.'), parent = MYAPP, i;

    // strip redundant leading global

    if (parts[0] === "MYAPP") {

        parts = parts.slice(1);

    }

    for ( i = 0; i < parts.length; i += 1) {

        // create a property if it doesn't exist

        if ( typeof parent[parts[i]] === "undefined") {

            parent[parts[i]] = {};

        }

        parent = parent[parts[i]];

    }

    return parent;

};

// assign returned value to a local var

var module2 = MYAPP.namespace('MYAPP.modules.module2');

module2 === MYAPP.modules.module2;
// true

// skip initial `MYAPP`

MYAPP.namespace('modules.module51');

// long namespace

MYAPP.namespace('once.upon.a.time.there.was.this.long.nested.property');

References:

JavaScript Patterns - by Stoyan Stefanov (O`Reilly)

JavaScript Patterns 5.1 Namespace Pattern

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