如何编写一个适用于Node.js，RequireJS以及没有它们的模块

Question

I am working on a JavaScript library for JSON/XML processing . My library works in browser as well as Node.js (with xmldom and xmlhttprequest modules).

One of the users recently asked for RequireJS support. I have taken a look at the RequireJS/AMD thing and think it is a good approach so I'd like to provide this.

However I'd like to retain the portability: my library must work in browsers (with and without RequireJS) as well as Node.js. And in the browser environment I don't depend on xmldom or xmlhttprequest since these things are provided by the browser itself.

My question is: how can I implement my library so that it works in browsers as well as in Node.js with an without RequireJS?

A bit of historyand my current solution

I initially wrote my library for browsers. So it just created a global-scope object and put everything inside it:

var Jsonix = { ... };

Later on users asked for Node.js support. So I added:

if(typeof require === 'function'){
    module.exports.Jsonix = Jsonix;
}

I also had to import few modules mentioned above. I did it conditionally, depending on whether the require function is available or not:

if (typeof require === 'function')
{
    var XMLHttpRequest = require('xmlhttprequest').XMLHttpRequest;
    return new XMLHttpRequest();
}

Now there's this story with RequireJS. If RequireJS is present then the require function is present as well. But module loading works differently, I have to use the define function etc. I also can't just require things since require has an async API in RequireJS. Moreover, if my library is loaded via RequireJS, it seems to process the source code and detects require('something') even if I do it conditionally like

if (typeof require === 'function' && typeof require.specified !== 'function) ...

RequireJS still detects require('xmlhttprequest') an tries to load the corresponding JS file.

Currently I'm coming to the following solution.

// Module factory function, AMD style
var _jsonix = function(_jsonix_xmldom, _jsonix_xmlhttprequest, _jsonix_fs)
{
    // Complete Jsonix script is included below 
    var Jsonix = { ... };
    // Complete Jsonix script is included above
    return { Jsonix: Jsonix };
};

// If require function exists ...
if (typeof require === 'function') {
    // ... but define function does not exists, assume we're in the Node.js environment
    // In this case, load the define function via amdefine
    if (typeof define !== 'function') {
        var define = require('amdefine')(module);
        define(["xmldom", "xmlhttprequest", "fs"], _jsonix);
    }
    else {
        // Otherwise assume we're in the RequireJS environment
        define([], _jsonix);
    }
}
// Since require function does not exists,
// assume we're neither in Node.js nor in RequireJS environment
// This is probably a browser environment
else
{
    // Call the module factory directly
    var Jsonix = _jsonix();
}

And this is how I check for dependencies now:

if (typeof _jsonix_xmlhttprequest !== 'undefined')
{
    var XMLHttpRequest = _jsonix_xmlhttprequest.XMLHttpRequest;
    return new XMLHttpRequest();
}

If I have require but not define then I assume this is a Node.js environment. I use amdefine to define the module and pass the required dependencies.

If I have require and define thet I assume this is a RequireJS environment, so I just use the define function. Currently I also assume this is a browser environment so dependencies like xmldom and xmlhttprequest are not available and don't require them. (This is probably nor correct.)

If I don't have the require function then I assume this is a browser environment without RequireJS/AMD support so I invoke the module factory _jsonix directly and export the result as a global object.

So, this is my approach so far. Seems a little bit awkward to me, and as a newbie to RequireJS/AMD I'm seeking advise. Is it the right approach? Are there better ways to address the problem? I'd be grateful for your help.

Answer 1

Take a look at how underscore.js handles it.

// Export the Underscore object for **Node.js**, with
// backwards-compatibility for the old `require()` API. If we're in
// the browser, add `_` as a global object.
if (typeof exports !== 'undefined') {
  if (typeof module !== 'undefined' && module.exports) {
    exports = module.exports = _;
  }
  exports._ = _;
} else {
  root._ = _;
}

...

// AMD registration happens at the end for compatibility with AMD loaders
// that may not enforce next-turn semantics on modules. Even though general
// practice for AMD registration is to be anonymous, underscore registers
// as a named module because, like jQuery, it is a base library that is
// popular enough to be bundled in a third party lib, but not be part of
// an AMD load request. Those cases could generate an error when an
// anonymous define() is called outside of a loader request.
if (typeof define === 'function' && define.amd) {
  define('underscore', [], function() {
    return _;
  });
}

Answer 2

This is what I ended up with:

// If the require function exists ...
if (typeof require === 'function') {
    // ... but the define function does not exists
    if (typeof define !== 'function') {
        // Assume we're in the Node.js environment
        // In this case, load the define function via amdefine
        var define = require('amdefine')(module);
        // Use xmldom and xmlhttprequests as dependencies
        define(["xmldom", "xmlhttprequest", "fs"], _jsonix_factory);
    }
    else {
        // Otherwise assume we're in the browser/RequireJS environment
        // Load the module without xmldom and xmlhttprequests dependencies
        define([], _jsonix_factory);
    }
}
// If the require function does not exists, we're not in Node.js and therefore in browser environment
else
{
    // Just call the factory and set Jsonix as global.
    var Jsonix = _jsonix_factory().Jsonix;
}

Answer 3

Here is a template I'm currently using, it's both AMD and node compatible though not directly loadable stand-alone in the browser...

The main advantage to this approach is that the domain-specific code does not need to care about what imported it, for the general case.

/**********************************************************************
* 
*
*
**********************************************************************/
((typeof define)[0]=='u'?function(f){module.exports=f(require)}:define)(
function(require){ var module={} // makes module AMD/node compatible...
/*********************************************************************/




/*********************************************************************/




/**********************************************************************
* vim:set ts=4 sw=4 :                               */ return module })