O/S is ubuntu 16, node version is 4.2.6.
I have source / development code and run / distribution code, the source.js files are minified and mangled to create equivalent source.min.js files, and I would like for node js require to automatically search for .min.js files as well as .js files.
But as I have a lot of files, I would prefer not to have to go through every require in every file and instead modify the built-in require() function.
This is a very simple implementation of a stand alone function, but how can I modify the built-in function to behave the same way ?
function require(file){
try{return require(file)}
catch(e){return require(file+='.min.js')}
}
You can achieve this by modifying prototype function require of Module class and apply it globally
Here is how you can do it :
var pathModule = require('path');
var assert = require('assert').ok;
module.constructor.prototype.require = function (path) {
var self = this;
assert(typeof path === 'string', 'path must be a string');
assert(path, 'missing path');
try {
return self.constructor._load(path, self);
} catch (err) {
// if module not found, we have nothing to do, simply throw it back.
if (err.code === 'MODULE_NOT_FOUND') {
throw err;
}
// resolve the path to get absolute path
path = pathModule.resolve(__dirname, path+".min.js")
// Write to log or whatever
console.log('Error in file: ' + path);
}
}
I have a node.js application with two typescript files.
matchmanager.ts is defined as -
namespace LobbyService
{
export class MatchManager
{
constructor() { /*code*/ }
}
}
and main.ts which is defined as
namespace LobbyService
{
let matchManager: MatchManager = new MatchManager() ;
/* code */
}
I setup visual studio to output the files into a single JS file called lobbyservice.js
However, when i type
node lobbyservice.js
I get the following error -
TypeError: LobbyService.MatchManager is not a constructor
The generated file has this output -
var LobbyService;
(function (LobbyService) {
var matchManager = new LobbyService.MatchManager();
})(LobbyService || (LobbyService = {}));
var LobbyService;
(function (LobbyService) {
var MatchManager = (function () {
function MatchManager() {
console.log("created");
}
return MatchManager;
}());
LobbyService.MatchManager = MatchManager;
})(LobbyService || (LobbyService = {}));
This was working before, but for some odd reason it isn't now. Any thoughts?
Update - I managed to get a version of the lobbyservice.js that works. For some odd reason, Visual studio transforms one version of the file into the one above, and one into this -
var LobbyService;
(function (LobbyService) {
var MatchManager = (function () {
function MatchManager() {
console.log("created");
}
return MatchManager;
}());
LobbyService.MatchManager = MatchManager;
})(LobbyService || (LobbyService = {}));
var LobbyService;
(function (LobbyService) {
var matchManager = new LobbyService.MatchManager();
})(LobbyService || (LobbyService = {}));
//# sourceMappingURL=lobby.js.map
No clue as to why i'm getting two different outputs like that for the same source code. Both projects have the same module property of "none"
So user Elliott highlighted that indeed it's a know typescript compile quirk where the order of the output javascript file creates an issue.
to fix that, i had to add
/// <reference path="matchmanager.ts"/>
On my typescript files that used MatchManager class, even though they were on the same namespace and compiled ok. This forced the typescript compiler to create a workable javascript output.
Assume that I have a nodeJS module whose index.js is as below
module.exports = function() {
var map = {},
CSV_FILE = "./input.csv",
_loadCSV = function() {
var fs = require('fs'),
parse = require('csv-parse'),
rawCSVData = fs.readFileSync(CSV_FILE).toString(),
i,
item;
parse(rawCSVData, {columns: true}, function(err, data) {
for (i = 0; i < data.length; i++) {
item = data[i];
map[item.key] = item.value;
}
});
},
_init = function() {
_loadCSV();
};
// Init
_init();
// Public
return {
/**
* getValue
*/
getValue: function(key) {
return map[key];
}
};
};
Now, everything works fine if I test locally. However, when I install this module in another project I get below error.
fs.js:549 return binding.open(pathModule._makeLong(path), stringToFlags(flags), mode);
^
Error: ENOENT: no such file or directory, open 'input.csv' at Error (native)
Is it possible to include a static mapping file as part of a nodeJS module that is used in module initialization?
Your problem is this line CSV_FILE = "./input.csv". It works locally because the script you're executing (index.js) is in the same directory as the input.csv-file. However, when you install it as a dependency, the input.csv-file is actually somewhere in ./node_modules/your-module/input.csv, hence your new index.js can't see any ./input.csv-file since it's not located in the same directory as the calling script.
There are two ways to solve this, the first one being the smartest in my opinion.
Do not distribute the input.csv-file. This is a very bad approach to building modules, and you should rather change your code so that your module accepts a path to a .csv-file that it loads. However your module may need static data, but in those cases it's smarter to just convert it to a JavaScript Object and include it directly.
Simply change one line of code,
from CSV_FILE = "./input.csv"
to CSV_FILE = __dirname + "/input.csv"
See documentation for __dirname
I have read the details on NodeJS site : https://nodejs.org/api/modules.html. I don't understand how modules work, and what are the minimal steps for creating a module, and how npm can help me.
How can I create a module?
How do I use a module?
What does putting it on npm mean?
Note: this is a self answered question, with the purpose of sharing knowledge as a canonical.
You can create a NodeJS module using one line of code:
//mymodule.js
module.exports = 3;
Then you can load the module, by using require:
//app.js
require('./mymodule.js')
I added './' because it is a module of one file. We will cover it later.
Now if you do for example:
var mymodule = require('./mymodule.js');
console.log(mymodule); // 3
You can replace the number 3, with a function, for example:
//mymodule.js:
module.exports = function () {
console.log('function inside the module');
};
Then you can use it:
var mymodule = require('./mymodule.js');
mymodule();
Private variables:
Every variable you define inside A module will be defined only inside it:
//mymodule.js
var myPrivateVariable = 3;
publicVariable = 5; // Never user global variables in modules
//It's bad-pracrtice. Always add: var.
module.exports = function() {
// Every function of the module can use the private variables
return myPrivateVariable++
};
//app.js
var mymodule = require('./mymodule.js');
console.log(mymodule()); // return 3
console.log(mymodule()); // return 4
Reuse modules:
One more thing you need to know about NodeJS modules, is that if you use the same module twice(require it), it will return the same instance, it will not run in twice.
for example:
//app.js
var mymodule1 = require('./mymodule.js');
var mymodule2 = require('./mymodule.js');
console.log(mymodule1()); //return 3
console.log(mymodule2()); //return 4 (not 3)
console.log(mymodule1()); //return 5
As you see in the example below, that private variable is shared between all the instances of the module.
A module package
If your module contain more than one file, or you want to share the module with others, you have to create the module in separate folder, and create a package.json file for the module.
npm init will create package.json file for you.
For modules, there are 3 required parts:
package.json
{
"name" : "You module name",
"version" : "0.0.3"
}
Now, you can publish the module, using npm publish. I recommend you publish all your modules to github as well, then the module will be connected to your github page.
What you publish to NPM will be accessible by everyone. So never publish modules that contain private data. For that you can use private npm modules.
Next steps
Modules can return more than one function or one variable. See this samples in which we return an object.
module.exports.a = function() {
// ..
};
module.exports.b = function() {
// ..
};
// OR
myObj = {
a:3,
b:function() {
return this.a;
}
};
module.exports = myObj;
More info:
Read about package.json files
Versioning in you modules best practice
More best practive for NodeJS modules
Private modules, using private npm
Related Questions:
What is the purpose of Node.js module.exports and how do you use it?
module.exports vs exports in Node.js
Creating module in node.js is pretty simple!!!
You may consider module as a set of functionalities you can use in other code by simply just requiring it.
for eg:Consider a file functional.js having the content:
function display(){
console.log('i am in a display function');
}
module.exports = display;
Now just require it in any other module like:
var display = require('./functional');
display()
Output:i am in a display function
Similarly you can do:
var exports = module.exports = {};
exports.display = function(){
console.log('i am in the display function');
}
or you do the same for objects like:
var funObj = {
hello:function(){
console.log('hello function');
},
display:function(){
console.log('display function');
}
};
module.exports = funObj;
There are two main ways for wiring modules. One of them is using hard coded dependencies, explicitly loading one module into another using a require call. The other method is to use a dependency injection pattern, where we pass the components as a parameter or we have a global container (known as IoC, or Inversion of Control container), which centralizes the management of the modules.
We can allow Node.js to manage the modules life cycle by using hard coded module loading. It organizes your packages in an intuitive way, which makes understanding and debugging easy.
Dependency Injection is rarely used in a Node.js environment, although it is a useful concept. The DI pattern can result in an improved decoupling of the modules. Instead of explicitly defining dependencies for a module, they are received from the outside. Therefore they can be easily replaced with modules having the same interfaces.
Let’s see an example for DI modules using the factory pattern:
class Car {
constructor (options) {
this.engine = options.engine
}
start () {
this.engine.start()
}
}
function create (options) {
return new Car(options)
}
module.exports = create
How do I require all files in a folder in node.js?
need something like:
files.forEach(function (v,k){
// require routes
require('./routes/'+v);
}};
When require is given the path of a folder, it'll look for an index.js file in that folder; if there is one, it uses that, and if there isn't, it fails.
It would probably make most sense (if you have control over the folder) to create an index.js file and then assign all the "modules" and then simply require that.
yourfile.js
var routes = require("./routes");
index.js
exports.something = require("./routes/something.js");
exports.others = require("./routes/others.js");
If you don't know the filenames you should write some kind of loader.
Working example of a loader:
var normalizedPath = require("path").join(__dirname, "routes");
require("fs").readdirSync(normalizedPath).forEach(function(file) {
require("./routes/" + file);
});
// Continue application logic here
I recommend using glob to accomplish that task.
var glob = require( 'glob' )
, path = require( 'path' );
glob.sync( './routes/**/*.js' ).forEach( function( file ) {
require( path.resolve( file ) );
});
Base on #tbranyen's solution, I create an index.js file that load arbitrary javascripts under current folder as part of the exports.
// Load `*.js` under current directory as properties
// i.e., `User.js` will become `exports['User']` or `exports.User`
require('fs').readdirSync(__dirname + '/').forEach(function(file) {
if (file.match(/\.js$/) !== null && file !== 'index.js') {
var name = file.replace('.js', '');
exports[name] = require('./' + file);
}
});
Then you can require this directory from any where else.
Another option is to use the package require-dir which let's you do the following. It supports recursion as well.
var requireDir = require('require-dir');
var dir = requireDir('./path/to/dir');
I have a folder /fields full of files with a single class each, ex:
fields/Text.js -> Test class
fields/Checkbox.js -> Checkbox class
Drop this in fields/index.js to export each class:
var collectExports, fs, path,
__hasProp = {}.hasOwnProperty;
fs = require('fs');
path = require('path');
collectExports = function(file) {
var func, include, _results;
if (path.extname(file) === '.js' && file !== 'index.js') {
include = require('./' + file);
_results = [];
for (func in include) {
if (!__hasProp.call(include, func)) continue;
_results.push(exports[func] = include[func]);
}
return _results;
}
};
fs.readdirSync('./fields/').forEach(collectExports);
This makes the modules act more like they would in Python:
var text = new Fields.Text()
var checkbox = new Fields.Checkbox()
One more option is require-dir-all combining features from most popular packages.
Most popular require-dir does not have options to filter the files/dirs and does not have map function (see below), but uses small trick to find module's current path.
Second by popularity require-all has regexp filtering and preprocessing, but lacks relative path, so you need to use __dirname (this has pros and contras) like:
var libs = require('require-all')(__dirname + '/lib');
Mentioned here require-index is quite minimalistic.
With map you may do some preprocessing, like create objects and pass config values (assuming modules below exports constructors):
// Store config for each module in config object properties
// with property names corresponding to module names
var config = {
module1: { value: 'config1' },
module2: { value: 'config2' }
};
// Require all files in modules subdirectory
var modules = require('require-dir-all')(
'modules', // Directory to require
{ // Options
// function to be post-processed over exported object for each require'd module
map: function(reqModule) {
// create new object with corresponding config passed to constructor
reqModule.exports = new reqModule.exports( config[reqModule.name] );
}
}
);
// Now `modules` object holds not exported constructors,
// but objects constructed using values provided in `config`.
I know this question is 5+ years old, and the given answers are good, but I wanted something a bit more powerful for express, so i created the express-map2 package for npm. I was going to name it simply express-map, however the people at yahoo already have a package with that name, so i had to rename my package.
1. basic usage:
app.js (or whatever you call it)
var app = require('express'); // 1. include express
app.set('controllers',__dirname+'/controllers/');// 2. set path to your controllers.
require('express-map2')(app); // 3. patch map() into express
app.map({
'GET /':'test',
'GET /foo':'middleware.foo,test',
'GET /bar':'middleware.bar,test'// seperate your handlers with a comma.
});
controller usage:
//single function
module.exports = function(req,res){
};
//export an object with multiple functions.
module.exports = {
foo: function(req,res){
},
bar: function(req,res){
}
};
2. advanced usage, with prefixes:
app.map('/api/v1/books',{
'GET /': 'books.list', // GET /api/v1/books
'GET /:id': 'books.loadOne', // GET /api/v1/books/5
'DELETE /:id': 'books.delete', // DELETE /api/v1/books/5
'PUT /:id': 'books.update', // PUT /api/v1/books/5
'POST /': 'books.create' // POST /api/v1/books
});
As you can see, this saves a ton of time and makes the routing of your application dead simple to write, maintain, and understand. it supports all of the http verbs that express supports, as well as the special .all() method.
npm package: https://www.npmjs.com/package/express-map2
github repo: https://github.com/r3wt/express-map
Expanding on this glob solution. Do this if you want to import all modules from a directory into index.js and then import that index.js in another part of the application. Note that template literals aren't supported by the highlighting engine used by stackoverflow so the code might look strange here.
const glob = require("glob");
let allOfThem = {};
glob.sync(`${__dirname}/*.js`).forEach((file) => {
/* see note about this in example below */
allOfThem = { ...allOfThem, ...require(file) };
});
module.exports = allOfThem;
Full Example
Directory structure
globExample/example.js
globExample/foobars/index.js
globExample/foobars/unexpected.js
globExample/foobars/barit.js
globExample/foobars/fooit.js
globExample/example.js
const { foo, bar, keepit } = require('./foobars/index');
const longStyle = require('./foobars/index');
console.log(foo()); // foo ran
console.log(bar()); // bar ran
console.log(keepit()); // keepit ran unexpected
console.log(longStyle.foo()); // foo ran
console.log(longStyle.bar()); // bar ran
console.log(longStyle.keepit()); // keepit ran unexpected
globExample/foobars/index.js
const glob = require("glob");
/*
Note the following style also works with multiple exports per file (barit.js example)
but will overwrite if you have 2 exports with the same
name (unexpected.js and barit.js have a keepit function) in the files being imported. As a result, this method is best used when
your exporting one module per file and use the filename to easily identify what is in it.
Also Note: This ignores itself (index.js) by default to prevent infinite loop.
*/
let allOfThem = {};
glob.sync(`${__dirname}/*.js`).forEach((file) => {
allOfThem = { ...allOfThem, ...require(file) };
});
module.exports = allOfThem;
globExample/foobars/unexpected.js
exports.keepit = () => 'keepit ran unexpected';
globExample/foobars/barit.js
exports.bar = () => 'bar run';
exports.keepit = () => 'keepit ran';
globExample/foobars/fooit.js
exports.foo = () => 'foo ran';
From inside project with glob installed, run node example.js
$ node example.js
foo ran
bar run
keepit ran unexpected
foo ran
bar run
keepit ran unexpected
One module that I have been using for this exact use case is require-all.
It recursively requires all files in a given directory and its sub directories as long they don't match the excludeDirs property.
It also allows specifying a file filter and how to derive the keys of the returned hash from the filenames.
Require all files from routes folder and apply as middleware. No external modules needed.
// require
const { readdirSync } = require("fs");
// apply as middleware
readdirSync("./routes").map((r) => app.use("/api", require("./routes/" + r)));
I'm using node modules copy-to module to create a single file to require all the files in our NodeJS-based system.
The code for our utility file looks like this:
/**
* Module dependencies.
*/
var copy = require('copy-to');
copy(require('./module1'))
.and(require('./module2'))
.and(require('./module3'))
.to(module.exports);
In all of the files, most functions are written as exports, like so:
exports.function1 = function () { // function contents };
exports.function2 = function () { // function contents };
exports.function3 = function () { // function contents };
So, then to use any function from a file, you just call:
var utility = require('./utility');
var response = utility.function2(); // or whatever the name of the function is
Can use : https://www.npmjs.com/package/require-file-directory
Require selected files with name only or all files.
No need of absoulute path.
Easy to understand and use.
Using this function you can require a whole dir.
const GetAllModules = ( dirname ) => {
if ( dirname ) {
let dirItems = require( "fs" ).readdirSync( dirname );
return dirItems.reduce( ( acc, value, index ) => {
if ( PATH.extname( value ) == ".js" && value.toLowerCase() != "index.js" ) {
let moduleName = value.replace( /.js/g, '' );
acc[ moduleName ] = require( `${dirname}/${moduleName}` );
}
return acc;
}, {} );
}
}
// calling this function.
let dirModules = GetAllModules(__dirname);
Create an index.js file in your folder with this code :
const fs = require('fs')
const files = fs.readdirSync('./routes')
for (const file of files) {
require('./'+file)
}
And after that you can simply load all the folder with require("./routes")
If you include all files of *.js in directory example ("app/lib/*.js"):
In directory app/lib
example.js:
module.exports = function (example) { }
example-2.js:
module.exports = function (example2) { }
In directory app create index.js
index.js:
module.exports = require('./app/lib');