Question

I want to use one module feature within another module

file main.js

var _ = require("./underscore.js");
var foo = require("./bar.js");
foo.publish(...);

file bar.js

(function(e) {
    var array = [...];
    e.publish = function(t, args) {
        _.each(array, function(...) {...});
    });
})(exports);

I’ve tried a couple of variations, but I am not sure of the best way around this error:

ReferenceError: _ is not defined

Answer 1

Yes, you should use in every module which needs that variable, for the case of you example.

var _ = require("./underscore.js");

But if you need to transfer one object instance between several modules you can use process object to make it global. But that is BAD practice.

process._ = require("./underscore.js");

Good way to pass object instances between the modules is to pass them as function arguments, but you need to change you bar.js to return a factory function, not an object itself.

module.exports = function(_) {
   var e = {};
   var array = [...];
   e.publish = function(t, args) {
      _.each(array, function(...) {...});
   });
   return e;
}

In main.js:

var _ = require("./underscore.js");
var foo = require("./bar.js")(_);
foo.publish(...);

I hope you got the point.