Load "Vanilla" Javascript Libraries into Node.js

Here's what I think is the 'rightest' answer for this situation.

Say you have a script file called quadtree.js.

You should build a custom node_module that has this sort of directory structure...

./node_modules/quadtree/quadtree-lib/
./node_modules/quadtree/quadtree-lib/quadtree.js
./node_modules/quadtree/quadtree-lib/README
./node_modules/quadtree/quadtree-lib/some-other-crap.js
./node_modules/quadtree/index.js

Everything in your ./node_modules/quadtree/quadtree-lib/ directory are files from your 3rd party library.

Then your ./node_modules/quadtree/index.js file will just load that library from the filesystem and do the work of exporting things properly.

var fs = require('fs');

// Read and eval library
filedata = fs.readFileSync('./node_modules/quadtree/quadtree-lib/quadtree.js','utf8');
eval(filedata);

/* The quadtree.js file defines a class 'QuadTree' which is all we want to export */

exports.QuadTree = QuadTree

Now you can use your quadtree module like any other node module...

var qt = require('quadtree');
qt.QuadTree();

I like this method because there's no need to go changing any of the source code of your 3rd party library--so it's easier to maintain. All you need to do on upgrade is look at their source code and ensure that you are still exporting the proper objects.

There is a much better method than using eval: the vm module.

For example, here is my execfile module, which evaluates the script at path in either context or the global context:

var vm = require("vm");
var fs = require("fs");
module.exports = function(path, context) {
  context = context || {};
  var data = fs.readFileSync(path);
  vm.runInNewContext(data, context, path);
  return context;
}

And it can be used like this:

> var execfile = require("execfile");
> // `someGlobal` will be a global variable while the script runs
> var context = execfile("example.js", { someGlobal: 42 });
> // And `getSomeGlobal` defined in the script is available on `context`:
> context.getSomeGlobal()
42
> context.someGlobal = 16
> context.getSomeGlobal()
16

Where example.js contains:

function getSomeGlobal() {
    return someGlobal;
}

The big advantage of this method is that you've got complete control over the global variables in the executed script: you can pass in custom globals (via context), and all the globals created by the script will be added to context. Debugging is also easier because syntax errors and the like will be reported with the correct file name.

The simplest way is: eval(require('fs').readFileSync('./path/to/file.js', 'utf8')); This works great for testing in the interactive shell.

AFAIK, that is indeed how modules must be loaded. However, instead of tacking all exported functions onto the exports object, you can also tack them onto this (what would otherwise be the global object).

So, if you want to keep the other libraries compatible, you can do this:

this.quadTree = function () {
  // the function's code
};

or, when the external library already has its own namespace, e.g. jQuery (not that you can use that in a server-side environment):

this.jQuery = jQuery;

In a non-Node environment, this would resolve to the global object, thus making it a global variable... which it already was. So it shouldn't break anything.

Edit: James Herdman has a nice writeup about node.js for beginners, which also mentions this.

Load "Vanilla" Javascript Libraries into Node.js

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