Accessing global variables with node.js and CoffeeScript - javascript

I'm trying to declare global variables for my applications that I'm writing using Node.js and CoffeeScript. So I'm declaring it in a common file that is concatenated to both applications after compilation. In that file I have for example:
root = exports ? this
root.myVariable = 300
So my first application is a HTML one. When I try to access this variable, for example by
console.log myVariable
There is no problem with it. But my other application is a server application lauched by node command and I cannot access that variable in that application. I tried:
console.log root.myVariable
console.log myVariable
With first line I'm getting 'undefined' printed (so it looks that root is defined) and with the second one, I'm getting ReferenceError - myVariable is undefined.
So how can I access this variable?
Here is an output code in Javascript that I get, I guess it might be helpful:
(function() {
var root, _ref;
root = (_ref = typeof module !== "undefined" && module !== null ? module.exports : void 0) != null ? _ref : this;
root.myVariable = 300;
}).call(this);
(function() {
console.log(root.myVariable);
console.log(myVariable);
}).call(this);

You're close, but you need to change things just a little bit
# config.coffee
module.exports =
foo: "bar"
hello: "world"
db:
user: alice
pass: password1
# lib/a.coffee
config = require "../config"
# lib/b.coffee
config = require "../config"
# lib/db.coffee
dbconfig = require("../config").db

Client and server JavaScript (or CoffeeScript) works differently. So, its a really difficult to write a module that'll work in both applications.
There is a lot of libraries to solve this problem, like RequireJS and Browserify.
But I have two simpler suggestions for your problem.
First one is to use JSON to store your global constants. On the server side you can simply require you JSON file:
root = require './config.json'
On the client side you may either parse it manually or serve it as pjson.
My second suggestion is to write really simple module that'll be compatible with both your applications. It'll look something like this:
root =
myVariable: 300
myOtherVariable: 400
modulte.exports = root if module?.parent?
This code should be compatible with both node.js require function and browser <script> tag.
Update:
I just reread you question and realized, that you've did almost as I suggested. But your code looks fine to me. You may try to use module.export instead of its alias exports, it may help:
root = modulte?.exports ? this
root.myVariable = 300
But, as I said, your code looks fine to me as well.

Related

Splitting the code(commands/events) in different files [duplicate]

I'm trying to get JavaScript to read/write to a PostgreSQL database. I found this project on GitHub. I was able to get the following sample code to run in Node.
var pg = require('pg'); //native libpq bindings = `var pg = require('pg').native`
var conString = "tcp://postgres:1234#localhost/postgres";
var client = new pg.Client(conString);
client.connect();
//queries are queued and executed one after another once the connection becomes available
client.query("CREATE TEMP TABLE beatles(name varchar(10), height integer, birthday timestamptz)");
client.query("INSERT INTO beatles(name, height, birthday) values($1, $2, $3)", ['Ringo', 67, new Date(1945, 11, 2)]);
client.query("INSERT INTO beatles(name, height, birthday) values($1, $2, $3)", ['John', 68, new Date(1944, 10, 13)]);
//queries can be executed either via text/parameter values passed as individual arguments
//or by passing an options object containing text, (optional) parameter values, and (optional) query name
client.query({
name: 'insert beatle',
text: "INSERT INTO beatles(name, height, birthday) values($1, $2, $3)",
values: ['George', 70, new Date(1946, 02, 14)]
});
//subsequent queries with the same name will be executed without re-parsing the query plan by postgres
client.query({
name: 'insert beatle',
values: ['Paul', 63, new Date(1945, 04, 03)]
});
var query = client.query("SELECT * FROM beatles WHERE name = $1", ['John']);
//can stream row results back 1 at a time
query.on('row', function(row) {
console.log(row);
console.log("Beatle name: %s", row.name); //Beatle name: John
console.log("Beatle birth year: %d", row.birthday.getYear()); //dates are returned as javascript dates
console.log("Beatle height: %d' %d\"", Math.floor(row.height/12), row.height%12); //integers are returned as javascript ints
});
//fired after last row is emitted
query.on('end', function() {
client.end();
});
Next I tried to make it run on a webpage, but nothing seemed to happen. I checked on the JavaScript console and it just says "require not defined".
So what is this "require"? Why does it work in Node but not in a webpage?
Also, before I got it to work in Node, I had to do npm install pg. What's that about? I looked in the directory and didn't find a file pg. Where did it put it, and how does JavaScript find it?
So what is this "require?"
require() is not part of the standard JavaScript API. But in Node.js, it's a built-in function with a special purpose: to load modules.
Modules are a way to split an application into separate files instead of having all of your application in one file. This concept is also present in other languages with minor differences in syntax and behavior, like C's include, Python's import, and so on.
One big difference between Node.js modules and browser JavaScript is how one script's code is accessed from another script's code.
In browser JavaScript, scripts are added via the <script> element. When they execute, they all have direct access to the global scope, a "shared space" among all scripts. Any script can freely define/modify/remove/call anything on the global scope.
In Node.js, each module has its own scope. A module cannot directly access things defined in another module unless it chooses to expose them. To expose things from a module, they must be assigned to exports or module.exports. For a module to access another module's exports or module.exports, it must use require().
In your code, var pg = require('pg'); loads the pg module, a PostgreSQL client for Node.js. This allows your code to access functionality of the PostgreSQL client's APIs via the pg variable.
Why does it work in node but not in a webpage?
require(), module.exports and exports are APIs of a module system that is specific to Node.js. Browsers do not implement this module system.
Also, before I got it to work in node, I had to do npm install pg. What's that about?
NPM is a package repository service that hosts published JavaScript modules. npm install is a command that lets you download packages from their repository.
Where did it put it, and how does Javascript find it?
The npm cli puts all the downloaded modules in a node_modules directory where you ran npm install. Node.js has very detailed documentation on how modules find other modules which includes finding a node_modules directory.
Alright, so let's first start with making the distinction between Javascript in a web browser, and Javascript on a server (CommonJS and Node).
Javascript is a language traditionally confined to a web browser with a limited global context defined mostly by what came to be known as the Document Object Model (DOM) level 0 (the Netscape Navigator Javascript API).
Server-side Javascript eliminates that restriction and allows Javascript to call into various pieces of native code (like the Postgres library) and open sockets.
Now require() is a special function call defined as part of the CommonJS spec. In node, it resolves libraries and modules in the Node search path, now usually defined as node_modules in the same directory (or the directory of the invoked javascript file) or the system-wide search path.
To try to answer the rest of your question, we need to use a proxy between the code running in the the browser and the database server.
Since we are discussing Node and you are already familiar with how to run a query from there, it would make sense to use Node as that proxy.
As a simple example, we're going to make a URL that returns a few facts about a Beatle, given a name, as JSON.
/* your connection code */
var express = require('express');
var app = express.createServer();
app.get('/beatles/:name', function(req, res) {
var name = req.params.name || '';
name = name.replace(/[^a-zA_Z]/, '');
if (!name.length) {
res.send({});
} else {
var query = client.query('SELECT * FROM BEATLES WHERE name =\''+name+'\' LIMIT 1');
var data = {};
query.on('row', function(row) {
data = row;
res.send(data);
});
};
});
app.listen(80, '127.0.0.1');
I noticed that whilst the other answers explained what require is and that it is used to load modules in Node they did not give a full reply on how to load node modules when working in the Browser.
It is quite simple to do. Install your module using npm as you describe, and the module itself will be located in a folder usually called node_modules.
Now the simplest way to load it into your app is to reference it from your html with a script tag which points at this directory. i.e if your node_modules directory is in the root of the project at the same level as your index.html you would write this in your index.html:
<script src="node_modules/ng"></script>
That whole script will now be loaded into the page - so you can access its variables and methods directly.
There are other approaches which are more widely used in larger projects, such as a module loader like require.js. Of the two, I have not used Require myself, but I think it is considered by many people the way to go.
It's used to load modules. Let's use a simple example.
In file circle_object.js:
var Circle = function (radius) {
this.radius = radius
}
Circle.PI = 3.14
Circle.prototype = {
area: function () {
return Circle.PI * this.radius * this.radius;
}
}
We can use this via require, like:
node> require('circle_object')
{}
node> Circle
{ [Function] PI: 3.14 }
node> var c = new Circle(3)
{ radius: 3 }
node> c.area()
The require() method is used to load and cache JavaScript modules. So, if you want to load a local, relative JavaScript module into a Node.js application, you can simply use the require() method.
Example:
var yourModule = require( "your_module_name" ); //.js file extension is optional
Necromancing.
IMHO, the existing answers leave much to be desired.
At first, it's very confusing.
You have a (nowhere defined) function "require", which is used to get modules.
And in said (CommonJS) modules, you can use require, exports and module, WITHOUT THEM EVER BEING DEFINED.
Not that it would be new that you could use undefined variables in JS, but you couldn't use an undefined function.
So it looks a little like magic at first.
But all magic is based on deception.
When you dig a little deeper, it turns out it is really quite simple:
Require is simply a (non-standard) function defined at global scope.
(global scope = window-object in browser, global-object in NodeJS).
Note that by default, the "require function" is only implemented in NodeJS, not in the browser.
Also, note that to add to the confusion, for the browser, there is RequireJS, which, despite the name containing the characters "require", RequireJS absolutely does NOT implement require/CommonJS - instead RequireJS implements AMD, which is something similar, but not the same (aka incompatible).
That last one is just one important thing you have to realize on your way to understanding require.
Now, as such, to answer the question "what is require", we "simply" need to know what this function does.
This is perhaps best explained with code.
Here's a simple implementation by Michele Nasti, the code you can find on his github page.
Let's call our minimalisc implementation of the require function "myRequire":
function myRequire(name)
{
console.log(`Evaluating file ${name}`);
if (!(name in myRequire.cache)) {
console.log(`${name} is not in cache; reading from disk`);
let code = fs.readFileSync(name, 'utf8');
let module = { exports: {} };
myRequire.cache[name] = module;
let wrapper = Function("require, exports, module", code);
wrapper(myRequire, module.exports, module);
}
console.log(`${name} is in cache. Returning it...`);
return myRequire.cache[name].exports;
}
myRequire.cache = Object.create(null);
window.require = myRequire;
const stuff = window.require('./main.js');
console.log(stuff);
Now you notice, the object "fs" is used here.
For simplicity's sake, Michele just imported the NodeJS fs module:
const fs = require('fs');
Which wouldn't be necessary.
So in the browser, you could make a simple implementation of require with a SYNCHRONOUS XmlHttpRequest:
const fs = {
file: `
// module.exports = \"Hello World\";
module.exports = function(){ return 5*3;};
`
, getFile(fileName: string, encoding: string): string
{
// https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Synchronous_and_Asynchronous_Requests
let client = new XMLHttpRequest();
// client.setRequestHeader("Content-Type", "text/plain;charset=UTF-8");
// open(method, url, async)
client.open("GET", fileName, false);
client.send();
if (client.status === 200)
return client.responseText;
return null;
}
, readFileSync: function (fileName: string, encoding: string): string
{
// this.getFile(fileName, encoding);
return this.file; // Example, getFile would fetch this file
}
};
Basically, what require thus does, is it downloads a JavaScript-file, evals it in an anonymous namespace (aka Function), with the parameters "require", "exports" and "module", and returns the exports, meaning an object's public functions and properties.
Note that this evaluation is recursive: you require files, which themselfs can require files.
This way, all "global" variables used in your module are variables in the require-wrapper-function namespace, and don't pollute the global scope with unwanted variables.
Also, this way, you can reuse code without depending on namespaces, so you get "modularity" in JavaScript. "modularity" in quotes, because this is not exactly true, though, because you can still write window.bla/global.bla, and hence still pollute the global scope... Also, this establishes a separation between private and public functions, the public functions being the exports.
Now instead of saying
module.exports = function(){ return 5*3;};
You can also say:
function privateSomething()
{
return 42:
}
function privateSomething2()
{
return 21:
}
module.exports = {
getRandomNumber: privateSomething
,getHalfRandomNumber: privateSomething2
};
and return an object.
Also, because your modules get evaluated in a function with parameters
"require", "exports" and "module", your modules can use the undeclared variables "require", "exports" and "module", which might be startling at first. The require parameter there is of course a pointer to the require function saved into a variable.
Cool, right ?
Seen this way, require looses its magic, and becomes simple.
Now, the real require-function will do a few more checks and quirks, of course, but this is the essence of what that boils down to.
Also, in 2020, you should use the ECMA implementations instead of require:
import defaultExport from "module-name";
import * as name from "module-name";
import { export1 } from "module-name";
import { export1 as alias1 } from "module-name";
import { export1 , export2 } from "module-name";
import { foo , bar } from "module-name/path/to/specific/un-exported/file";
import { export1 , export2 as alias2 , [...] } from "module-name";
import defaultExport, { export1 [ , [...] ] } from "module-name";
import defaultExport, * as name from "module-name";
import "module-name";
And if you need a dynamic non-static import (e.g. load a polyfill based on browser-type), there is the ECMA-import function/keyword:
var promise = import("module-name");
note that import is not synchronous like require.
Instead, import is a promise, so
var something = require("something");
becomes
var something = await import("something");
because import returns a promise (asynchronous).
So basically, unlike require, import replaces fs.readFileSync with fs.readFileAsync.
async readFileAsync(fileName, encoding)
{
const textDecoder = new TextDecoder(encoding);
// textDecoder.ignoreBOM = true;
const response = await fetch(fileName);
console.log(response.ok);
console.log(response.status);
console.log(response.statusText);
// let json = await response.json();
// let txt = await response.text();
// let blo:Blob = response.blob();
// let ab:ArrayBuffer = await response.arrayBuffer();
// let fd = await response.formData()
// Read file almost by line
// https://developer.mozilla.org/en-US/docs/Web/API/ReadableStreamDefaultReader/read#Example_2_-_handling_text_line_by_line
let buffer = await response.arrayBuffer();
let file = textDecoder.decode(buffer);
return file;
} // End Function readFileAsync
This of course requires the import-function to be async as well.
"use strict";
async function myRequireAsync(name) {
console.log(`Evaluating file ${name}`);
if (!(name in myRequireAsync.cache)) {
console.log(`${name} is not in cache; reading from disk`);
let code = await fs.readFileAsync(name, 'utf8');
let module = { exports: {} };
myRequireAsync.cache[name] = module;
let wrapper = Function("asyncRequire, exports, module", code);
await wrapper(myRequireAsync, module.exports, module);
}
console.log(`${name} is in cache. Returning it...`);
return myRequireAsync.cache[name].exports;
}
myRequireAsync.cache = Object.create(null);
window.asyncRequire = myRequireAsync;
async () => {
const asyncStuff = await window.asyncRequire('./main.js');
console.log(asyncStuff);
};
Even better, right ?
Well yea, except that there is no ECMA-way to dynamically import synchronously (without promise).
Now, to understand the repercussions, you absolutely might want to read up on promises/async-await here, if you don't know what that is.
But very simply put, if a function returns a promise, it can be "awaited":
"use strict";
function sleep(interval)
{
return new Promise(
function (resolve, reject)
{
let wait = setTimeout(function () {
clearTimeout(wait);
//reject(new Error(`Promise timed out ! (timeout = ${timeout})`));
resolve();
}, interval);
});
}
The promise would then normally be used like this:
function testSleep()
{
sleep(3000).then(function ()
{
console.log("Waited for 3 seconds");
});
}
But when you return a promise, you can also use await, which means we get rid of the callback (sort of - actually, it is being replaced with a state-machine in the compiler/interpreter).
This way, we make asynchronous code feel like synchronous, so we now can use try-catch for error-handling.
Note that if you want to use await in a function, that function must be declared async (hence async-await).
async function testSleep()
{
await sleep(5000);
console.log("i waited 5 seconds");
}
And also please note that in JavaScript, there is no way to call an async function (blockingly) from a synchronous one (the ones you know). So if you want to use await (aka ECMA-import), all your code needs to be async, which most likely is a problem, if everything isn't already async...
An example of where this simplified implementation of require fails, is when you require a file that is not valid JavaScript, e.g. when you require css, html, txt, svg and images or other binary files.
And it's easy to see why:
If you e.g. put HTML into a JavaScript function body, you of course rightfully get
SyntaxError: Unexpected token '<'
because of Function("bla", "<doctype...")
Now, if you wanted to extend this to for example include non-modules, you could just check the downloaded file-contents for code.indexOf("module.exports") == -1, and then e.g. eval("jquery content") instead of Func (which works fine as long as you're in the browser). Since downloads with Fetch/XmlHttpRequests are subject to the same-origin-policy, and integrity is ensured by SSL/TLS, the use of eval here is rather harmless, provided you checked the JS files before you added them to your site, but that much should be standard-operating-procedure.
Note that there are several implementations of require-like functionality:
the CommonJS (CJS) format, used in Node.js, uses a require function and module.exports to define dependencies and modules. The npm ecosystem is built upon this format. (this is what is implemented above)
the Asynchronous Module Definition (AMD) format, used in browsers, uses a define function to define modules. (basically, this is overcomplicated archaic crap that you wouldn't ever want to use). Also, AMD is the format that is implemented by RequireJS (note that despite the name containing the characters "require", AMD absolutely is NOT CommonJS).
the ES Module (ESM) format. As of ES6 (ES2015), JavaScript supports a native module format. It uses an export keyword to export a module’s public API and an import keyword to import it. This is the one you should use if you don't give a flying f*ck about archaic browsers, such as Safari and IE/EdgeHTML.
the System.register format, designed to support ES6 modules within ES5. (the one you should use, if you need support for older browsers (Safari & IE & old versions of Chrome on mobile phones/tablets), because it can load all formats [for some, plugins are required], can handle cyclic-dependencies, and CSS and HTML - don't define your modules as system.register, though - the format is rather complicated, and remember, it can read the other easier formats)
the Universal Module Definition (UMD) format, compatible to all the above mentioned formats (except ECMA), used both in the browser and in Node.js. It’s especially useful if you write modules that can be used in both NodeJS and the browser. It's somewhat flawed, as it doesn't support the latest ECMA modules, though (maybe this will get fixed) - use System.register instead.
Important sidenote on the function argument "exports":
JavaScript uses call-by-value-sharing - meaning objects are passed as a pointer, but the pointer-value itselfs is passed BY VALUE, not by reference. So you can't override exports by assigning it a new object. Instead, if you want to override exports, you need to assign the new object to module.exports - because hey, module is the pointer passed by value, but exports in module.exports is the reference to the original exports pointer.
Important sidenote on module-Scope:
Modules are evaluated ONCE, and then cached by require.
That means all your modules have a Singleton scope.
If you want a non-singleton scope, you have to do something like:
var x = require("foo.js").createInstance();
or simply
var x = require("foo.js")();
with appropriate code returned by your module.
If you need CommonJS-support for the browser (IE5+, Chrome, Firefox),
check out my code in my comment on Michele Nasti's project
You know how when you are running JavaScript in the browser, you have access to variables like "window" or Math? You do not have to declare these variables, they have been written for you to use whenever you want.
Well, when you are running a file in the Node.js environment, there is a variable that you can use. It is called "module" It is an object. It has a property called "exports." And it works like this:
In a file that we will name example.js, you write:
example.js
module.exports = "some code";
Now, you want this string "some code" in another file.
We will name the other file otherFile.js
In this file, you write:
otherFile.js
let str = require('./example.js')
That require() statement goes to the file that you put inside of it, finds whatever data is stored on the module.exports property. The let str = ... part of your code means that whatever that require statement returns is stored to the str variable.
So, in this example, the end-result is that in otherFile.js you now have this:
let string = "some code";
or -
let str = ('./example.js').module.exports
Note:
the file-name that is written inside of the require statement: If it is a local file, it should be the file-path to example.js. Also, the .js extension is added by default, so I didn't have to write it.
You do something similar when requiring node.js libraries, such as Express. In the express.js file, there is an object named 'module', with a property named 'exports'.
So, it looks something like along these lines, under the hood (I am somewhat of a beginner so some of these details might not be exact, but it's to show the concept:
express.js
module.exports = function() {
//It returns an object with all of the server methods
return {
listen: function(port){},
get: function(route, function(req, res){}){}
}
}
If you are requiring a module, it looks like this:
const moduleName = require("module-name");
If you are requiring a local file, it looks like this:
const localFile = require("./path/to/local-file");
(notice the ./ at the beginning of the file name)
Also note that by default, the export is an object .. eg module.exports = {} So, you can write module.exports.myfunction = () => {} before assigning a value to the module.exports. But you can also replace the object by writing module.exports = "I am not an object anymore."
Two flavours of module.exports / require:
(see here)
Flavour 1
export file (misc.js):
var x = 5;
var addX = function(value) {
return value + x;
};
module.exports.x = x;
module.exports.addX = addX;
other file:
var misc = require('./misc');
console.log("Adding %d to 10 gives us %d", misc.x, misc.addX(10));
Flavour 2
export file (user.js):
var User = function(name, email) {
this.name = name;
this.email = email;
};
module.exports = User;
other file:
var user = require('./user');
var u = new user();

Load text as JavaScript object in Node.js

I have a javascript file for node.js:
module.exports = {
someString: 'blblalb'
}
I want to able to read the file as a javascript object, using fs.readFileSync. I can't use require because I am using a variable that may be modified in runtime to load the file.
Is that possible?
You can use eval('JavaScript string') but is highly recommended not to. It is a serious security risk if you cannot 100% trust the source of the text. If a malicious user figures out a way to modify the text they have complete control of your system. It is not a path I would take or recommend.
const text = 'console.log("Hello")';
eval(text);
If I saw that code when I was doing a code review we would definitely be having some words.
it's possible to evaluate a file or string variable as child module in hacky yet valid way.
The problem is that Node.js module environment should be unaware of these operations. Child module may load other modules and contain require(...), it will fail if there is no require function (there is none if it is evaluated with vm) or it uses wrong module relative path (this will happen with eval), also there will be no dedicated module.exports for a module. This can be fixed by wrapping module source with Node.js module wrapper that was rewired to match child module location.
const fs = require('fs');
const Module = require('module');
const path = require('path');
const childModuleAbsPath = path.resolve('./foo/bar.js');
const childModuleBody = fs.readFileSync(childModuleAbsPath);
const childModuleObj = { exports: {} };
const { dir: childModuleDirname, base: childModuleFilename } = path.parse(childModuleAbsPath);
const childRequire = modulePath => module.require(childModuleAbsPath);
require('vm').runInThisContext(Module.wrap(childModuleBody))(
childModuleObj.exports,
childRequire,
childModuleObj,
childModuleDirname,
childModuleFilename
);
In this case childModuleObj.exports.someString === 'blblalb' after bar child module was evaluated.
This is XY problem that should be addressed in another way.
If the intention is to reevaluate a module with new variables, this can be done by invalidating Node module cache by modifying require.cache, e.g. with decache:
decache('./foo/bar');
const reloadedBar = require('./foo/bar');

creating a global object in nodejs accessible by .js modules

My nodejs project requires memory tables accessible by different .js module. Some modules will update the tables but the data must be the same across all modules(sort of a in memory db). As such, I need a truly global object....not a global per module object. Creating a common.js file with all the objects then require it in all the modules will not do since the data will be global/local to the respective modules. I have seen reference to nodejs globals where global.myobject would be global to all modules but the documentation is not clear as to whether this is so or not. The last discussion I saw was from 2014. Can anyone update me on what is the current situation? How is this problem solved?
In node.js..
if you had a module called common.js, that looked like this..
'use strict';
var obj = {};
module.exports = obj;
And then inside another module you did this
'use strict';
var c = require('./common');
c.test = 1234;
Then later another module did this..
'use strict';
var c = require('./common');
console.log(c);
//output = { test: 1234 }
A module in modejs, is just another object. nodejs, caches any requires, and so will always return the same object.
One gotcha for windows users, windows filenames are not case-sensitive, so if you did require('Common'), and then did require('common'); you would have 2 version of the same module. And this is a good reason to keep all modules names in lowercase.

node.js global configuration

I'm currently working on a small console project that depends a lot on the arguments that are passed initially and I'm looking for a good way to handle a configuration object in nodejs.
I have the project currently fully working with the following example but I think I'm relaying on the caching of modules when using 'require'.
lets assume a module options.js
'use strict';
var options = {
configName: '.jstail',
colorActive: (process.platform === 'win32') ? false : true, // deactivate color by default on windows platform
quiet: false,
debug: false,
config: null,
logFile: null,
setting: null
};
module.exports = options;
And my initial module init.js
#!/usr/bin/env node
'use strict';
var options = require('options'); // require above options module
// modify the options object based on args
I then have a logger that depends on this options
For example if quiet is set to true no logging should happen
logger.js
'use strict';
var options = require('options');
/**
* prints to console if not explicitly suppresed
* #param {String} text
*/
function log(text) {
if (!options.quiet) {
console.log('[LOG]: ' + text);
}
}
My big problem is (I think) that I'm relaying on the caching of nodejs modules when I require the options module in the logger
So my two questions are:
Am I right that this only works because of the caching of the modules that nodejs does for me?
Is there any better way to handle a dynamic global configuration?
I know there are several questions and tutorials around with a config file but thats not what I'm looking for.
Yes, this only works because of caching, though I wouldn't call it caching (but node.js docs do) rather than lazy initialization. It's ok to rely on that, a lot of modules do some initialization of first require, using it for configuration is also typical. Generally speaking, require is a node.js way of accessing global singleton objects.
The other way to do it is to load configuration from a single file, modify it and then pass it to other modules who need it, like this:
//index.js
var config = require('./config')
config.flag = false
var module1 = require('./module1')(config)
//module1.js
module.exports = function (config) {
// do stuff
}
It makes code more decoupled and testable but adds complexity. Difference between these two approaches is basically the same as using globals vs dependency injection. Use whatever you like.

How to reuse commonjs modules in the browser and server using modulr?

I'm using modulr for using commonjs modules in the browser.
The goal is to be able to reuse some of those modules also in a server environment.
These "shared" modules need to do something like this:
var _ = _ || require("underscore");
meaning:
if _ exists as a global var (browser environment), use it
else load the "underscore" module (server), and use it instead
Now, since modulr does static analysis in all the code, looking for the require calls in order to generate the final js file, it will fail the build.
Is there a way to work around this problem?
(For example, if modulr supported something like --ignore=<module_list> parameter, everything would run fine.)
Apparently there's no way to fix this in modulr, so I had to create a workaround module named Env which looks like this:
// Env.js
var my = {
modules: undefined,
require: require
};
exports.override = function(modules) {
my.modules = modules;
};
exports.require = function(path) {
if (my.modules && my.modules[path]) {
return my.modules[path];
} else {
// my.require(...) is needed instead of simply require(...)
// because simply require(...) will cause a modulr parsing failure
return my.require(path);
}
};
And at the client side, have a specific initializer that does:
// ClientInitializer.js
Env = require('shared/Env');
Env.override({ underscore: _ });
So, the "shared" modules can do:
// SharedModule.js
var _ = require('shared/Env').require('underscore');
If the "shared" module is running in the server, the normal require function is called.
If it is running in the browser, the Env module will answer with the global _ variable.

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