Question

I’m trying to add a define module method to my top-level namespace, which first defines the namespace. For example,

APP.define('modules.moduleName', function () { 
    return {name: 'Module 1' }; 
});

But it seems that with my implementation of it, there is an assignment problem. Here is a simplified example of my implementation.

var APP = APP || {};
APP.namespace = function( nsString ) {

    var parts  = nsString.split('.'),
        parent = this,
        i;

    if (parts[0] === 'APP') {
        parts = parts.slice(1);
    }

    for ( i = 0; i < parts.length; i++ ) {
        if (typeof parent[parts[i]] === 'undefined') {
            parent[parts[i]] = {};
        }
        parent = parent[parts[i]];
    }

    return parent;
};

// Simplified example of my define function
APP.define = function( name, definition ) {
    var namespace = APP.namespace( name );

    namespace     = definition();
    return namespace;
};

// Example Module
APP.define('modules.example', function () {

    return {
        name   : 'Application',
        module : 'APP.module'
    };
});

However, it seems namespace is not assigned under the APP namespace after assigning it to definition(). However var module = APP.define('module.example', function () { /*...*/ }) works. This also works:

APP.define = function( name, definition ) {
    var namespace = APP.namespace( name );
    var module    = definition();

    for (var prop in module) {
        if (module.hasOwnProperty[prop]) {
            namespace[prop] = module[prop];
        }
    }
    return namespace;
};

There must be something about object reference or callback scope I’m missing.

Answer 1

When you assign var namespace to APP.namespace( name ) you get last part of namespace by reference, but then that namespace = definition() just redefines your namespace variable to result of definition function.

You can merge your APP.namespace and APP.define so your pre-last parent assigns last part of namespace as property to definition function

The code is:

var APP = APP || {};
APP.define = function( nsString, definition) {

    var parts  = nsString.split('.'),
        parent = this,
        i;

    if (parts[0] === 'APP') {
        parts = parts.slice(1);
    }

    for ( i = 0; i < parts.length - 1; i++ ) {
        if (typeof parent[parts[i]] === 'undefined') {
            parent[parts[i]] = {};
        }
        parent = parent[parts[i]];
    }

    parent[parts.pop()] = definition();
};