node.js: Accessing local variables from another module

javascript, node-modules, node.js, serverside-javascript

Solution

you should probably mostly never have to do this, but there might be reasons.

you can hook the loader and inject javascript code to export what you want.

// let's say you have node_modules/foreignmodule/index.js
// and in that script there is a local (not-exported) function foreignfunction().

var path = require('path');
_oldLoader = require.extensions['.js'];
require.extensions['.js'] = function(mod, filename) {
    if (filename == path.resolve(path.dirname(module.filename), 'node_modules/foreignmodule/index.js')) {
        var content = require('fs').readFileSync(filename, 'utf8');
        content += "module.exports.foreignfunction=foreignfunction;\n";
        mod._compile(content, filename);
    } else {
        _oldLoader(mod, filename);
    }
};

require('foreignmodule').foreignfunction();

Problem

My Problem I'm writing a `node` module called `a`, which `require()`s a module `b` (written by a stranger). Unfortunately, `a` doesn't only need to access the public members - it also needs to access local variables declared in the scope of the module. ``` // a var b = require('b'); console.log(b.public); console.log(b.private); // undefined // b var c = require('c'); var stdin = process.stdin; exports.public = true; var private = true; ``` My Solution ``` // a var b = require('b'); var srcPath = require.resolve('b'); console.log(b.public); fs.readFile(srcPath, 'utf-8', function (err, src) { var box = {}; var res = vm.runInNewContext(src, box, srcPath); console.log(box.private); }); ``` But `vm` doesn't run `b` as a module, so `require()` etc. aren't accessible from the context of the `vm`. So there are `ReferenceError`s like: ``` var res = vm.runInNewContext(src, box, scPath); ^ ReferenceError: require is not defined at <module b> at <module a> at fs.readFile (fs.js:176:14) at Object.oncomplete (fs.js:297:15) ``` My Question Which is the cleanest way to get the value of a local variable declared in another module? Ideas? Thanks for your help.

Original source