amdefine

What is amdefine?

The amdefine package is an implementation of the AMD (Asynchronous Module Definition) API for Node.js and an environment that does not natively support it. This allows developers to write their modules in a format that is both compatible with AMD-compatible loaders like RequireJS in the browser and usable in Node.js directly. It is particularly useful for projects that aim to share code between the client and the server or for projects that started in the browser and are moving to Node.js.

What are amdefine's main functionalities?

Module Definition

This feature allows the definition of modules in a way that's compatible with AMD. It checks if the `define` function is already present, and if not, it uses amdefine to provide it. This makes the module usable in environments that do not have native AMD support.

if (typeof define !== 'function') { var define = require('amdefine')(module) }
define(function(require) {
  var dependency = require('dependency');
  return function() {};
});

Dependency Injection

amdefine supports the AMD pattern of injecting dependencies as an array of strings, which are then provided as arguments to the module factory function. This simplifies managing dependencies and makes the module more modular and testable.

define(['dependency1', 'dependency2'], function(dependency1, dependency2) {
  // Module code that uses dependency1 and dependency2
});

Other packages similar to amdefine

requirejs

RequireJS is a more comprehensive solution for AMD module loading both on the client-side and server-side. It includes a loader for managing dependencies and optimizing them for production. Compared to amdefine, RequireJS offers a broader set of features for managing module dependencies and optimizing them for deployment.

browserify

Browserify allows you to use Node.js-style `require()` to organize your browser code and load modules installed by npm. It differs from amdefine by focusing on compiling Node.js modules for use in the browser rather than providing AMD compatibility. However, it serves a similar purpose of making code shareable between server and client environments.

webpack

Webpack is a powerful module bundler that can transform front-end assets like HTML, CSS, and JavaScript. It supports a variety of module definitions, including AMD, CommonJS, and ES6 modules, making it more versatile than amdefine. Webpack also includes a wide range of plugins and loaders that allow for complex build processes and optimizations.

README

amdefine

A module that can be used to implement AMD's define() in Node. This allows you to code to the AMD API and have the module work in node programs without requiring those other programs to use AMD.

Usage

1) Update your package.json to indicate amdefine as a dependency:

    "dependencies": {
        "amdefine": ">=0.1.0"
    }

Then run npm install to get amdefine into your project.

2) At the top of each module that uses define(), place this code:

if (typeof define !== 'function') { var define = require('amdefine')(module) }

Only use these snippets when loading amdefine. If you preserve the basic structure, with the braces, it will be stripped out when using the RequireJS optimizer.

You can add spaces, line breaks and even require amdefine with a local path, but keep the rest of the structure to get the stripping behavior.

As you may know, because if statements in JavaScript don't have their own scope, the var declaration in the above snippet is made whether the if expression is truthy or not. If RequireJS is loaded then the declaration is superfluous because define is already already declared in the same scope in RequireJS. Fortunately JavaScript handles multiple var declarations of the same variable in the same scope gracefully.

If you want to deliver amdefine.js with your code rather than specifying it as a dependency with npm, then just download the latest release and refer to it using a relative path:

Latest Version

amdefine/intercept

Consider this very experimental.

Instead of pasting the piece of text for the amdefine setup of a define variable in each module you create or consume, you can use amdefine/intercept instead. It will automatically insert the above snippet in each .js file loaded by Node.

Warning: you should only use this if you are creating an application that is consuming AMD style defined()'d modules that are distributed via npm and want to run that code in Node.

For library code where you are not sure if it will be used by others in Node or in the browser, then explicitly depending on amdefine and placing the code snippet above is suggested path, instead of using amdefine/intercept. The intercept module affects all .js files loaded in the Node app, and it is inconsiderate to modify global state like that unless you are also controlling the top level app.

Why distribute AMD-style modules via npm?

npm has a lot of weaknesses for front-end use (installed layout is not great, should have better support for the `baseUrl + moduleID + '.js' style of loading, single file JS installs), but some people want a JS package manager and are willing to live with those constraints. If that is you, but still want to author in AMD style modules to get dynamic require([]), better direct source usage and powerful loader plugin support in the browser, then this tool can help.

amdefine/intercept usage

Just require it in your top level app module (for example index.js, server.js):

require('amdefine/intercept');

The module does not return a value, so no need to assign the result to a local variable.

Then just require() code as you normally would with Node's require(). Any .js loaded after the intercept require will have the amdefine check injected in the .js source as it is loaded. It does not modify the source on disk, just prepends some content to the text of the module as it is loaded by Node.

How amdefine/intercept works

It overrides the Module._extensions['.js'] in Node to automatically prepend the amdefine snippet above. So, it will affect any .js file loaded by your app.

define() usage

It is best if you use the anonymous forms of define() in your module:

define(function (require) {
    var dependency = require('dependency');
});

or

define(['dependency'], function (dependency) {

});

RequireJS optimizer integration.

Version 1.0.3 of the RequireJS optimizer will have support for stripping the if (typeof define !== 'function') check mentioned above, so you can include this snippet for code that runs in the browser, but avoid taking the cost of the if() statement once the code is optimized for deployment.

Node 0.4 Support

If you want to support Node 0.4, then add require as the second parameter to amdefine:

//Only if you want Node 0.4. If using 0.5 or later, use the above snippet.
if (typeof define !== 'function') { var define = require('amdefine')(module, require) }

Limitations

Synchronous vs Asynchronous

amdefine creates a define() function that is callable by your code. It will execute and trace dependencies and call the factory function synchronously, to keep the behavior in line with Node's synchronous dependency tracing.

The exception: calling AMD's callback-style require() from inside a factory function. The require callback is called on process.nextTick():

define(function (require) {
    require(['a'], function(a) {
        //'a' is loaded synchronously, but
        //this callback is called on process.nextTick().
    });
});

Loader Plugins

Loader plugins are supported as long as they call their load() callbacks synchronously. So ones that do network requests will not work. However plugins like text can load text files locally.

The plugin API's load.fromText() is not supported in amdefine, so this means transpiler plugins like the CoffeeScript loader plugin will not work. This may be fixable, but it is a bit complex, and I do not have enough node-fu to figure it out yet. See the source for amdefine.js if you want to get an idea of the issues involved.

Tests

To run the tests, cd to tests and run:

node all.js
node all-intercept.js

License

New BSD and MIT. Check the LICENSE file for all the details.