Call function of app.js from within module in node.js?

Question

Let's say I have the following app.js (obviously very simplified):

var express = require('express'),
    app = express.createServer();

// include routes
require('./lib/routes')(app);

// some random function
var foo = function() {
    return 'bar';
};

// another random function
var foo2 = function() {
    return 'bar2';
};

And then I have the routes module:

module.exports = function(app){
    app.get('/some/route', function(req, res){
        var fooBar = foo(),
            fooBar2 = foo2();

        res.end(fooBar + fooBar2);
    });
};

This obviously doesn't work since foo and foo2 weren't defined within the module. Is there a way to make this work, or at least a different pattern to better accomplish what this?

Farid Nouri Neshat · Accepted Answer · 2014-06-13 08:38:36Z

7

Well you can just put these two functions in an object and pass them on the initialization of the routes.js .

var express = require('express'),
    app = express.createServer();

// some random function
var foo = function() {
    return 'bar';
};

// another random function
var foo2 = function() {
    return 'bar2';
};

var fns = {foo : foo, foo2: foo2}

// include routes
require('./lib/routes')(app, fns);

in routes:

module.exports = function(app, fns){
    app.get('/some/route', function(req, res){
        var fooBar = fns.foo(),
            fooBar2 = fns.foo2();

        res.end(fooBar + fooBar2);
    });
};

This is how would I do it. You can also include them in the app object. Beside passing them in init functions, you can also export those two functions and require them in routes.js.

var express = require('express'),
    app = express.createServer();

// some random function
var foo = function() {
    return 'bar';
};

// another random function
var foo2 = function() {
    return 'bar2';
};

module.exports = {foo : foo, foo2: foo2}

// include routes
require('./lib/routes')(app, fns);

in routes:

module.exports = function(app){
    var fns = require('../app.js');
    app.get('/some/route', function(req, res){
        var fooBar = fns.foo(),
            fooBar2 = fns.foo2();

        res.end(fooBar + fooBar2);
    });
};

But I don't like the idea of it, since it makes circular dependencies. Don't have any good feelings about them.

edited Jun 13, 2014 at 8:38

answered Jan 27, 2012 at 1:45

Farid Nouri Neshat

30.5k6 gold badges80 silver badges128 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

unsynchronized Over a year ago

Both the original question, and this accepted answer imply that module.exports is a function that is called. It's not. It's an object that contains functions. Also both the question and this answer have a trailing ")" after the closing brace for the definition. Eg module.exports = function(app){..}) - For one thing this would never execute. For another, it should be something like module.exports.myfunc = function(args) {...} OR module.exports = { myfunc1 : function(){...}, myfunc2: function(){...} }; Ok it's an old question, but for the sake of newbies, it needs clarification.

Farid Nouri Neshat Over a year ago

The closing brace was a mistake. module.exports can be set to a function. It's called substack pattern unofficially. Check it out.

unsynchronized Over a year ago

i realize it can be set to anything you like, including a random number. it all depends if you want to follow a standard, or just hack about, not caring if anyone wants to use your code. you could after all just not use modules at all. the whole point is to follow a convention. if you were planning on doing that, an acceptable way would be to export an object or function called substack, which does whatever you want.

unsynchronized Over a year ago

as an experiment, try this: "console.log(module);" see what it prints out. its has an empty {} for exports. that's the standard. you then go ahead and populate it, not blow it away and replace it with a function/number/string/date object. if you need to export other things, put them inside the exports object. that's how it's been designed to be be used.

Farid Nouri Neshat Over a year ago

Actually whenever you want to export one function only, this method is used. In some cases, I've seen people adding properties to the function(function main() {...};main.minorThing = function () {...}; module.exports = main). This is a very common pattern. Node.js assert module also exports a main function as I described above. Looking at the first page of npm registry, in the top modules, request, express, socket.io and mkdirp all use this pattern.

|

Collectives™ on Stack Overflow

Call function of app.js from within module in node.js?

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related