Node.js information and cheatsheets.
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Node.js Cheat

Node.js information and cheatsheets.

General JavaScript information will not be discussed here: only Node.js differences. For a JavaScript cheat see:

  1. index
  2. HTTP
  3. setTimeout

What is Node.js

Node is JavaScript interpreted / compiled by Google's open source V8 JavaScript engine used in Chrome:, official Git mirror at: outside of browsers.

It transforms JavaScript into a language + stdlib comparable to Python or Ruby.

It is often used on server side applications, although it already has many client applications as well.

V8 implements all of ECMAScript 5, so you can use all of it, including things which you should not usually use from browsers because some browsers don't implement them.

Since it is run from outside the browser, built-in objects such as document and window which represent web page concepts are not defined. That those built-in objects are not defined as part of ECMAScript.

Node does add other built-ins and a file require system. These add functionality which is often implemented in the stdlib of other languages like Python or Ruby, such as file IO, and cannot be provided by in-browser JavaScript for security concerns.

Node gives great importance to parallel processing, because its development is closely related with web development, where requests are often made over the network and always take a very large time to complete. Many methods have both synchronous and asynchronous versions, including filesystem IO.

Common js

Informal standard that aims at standardizing the API for JavaScript outside of browsers:

Node implements it.

It specifies things like: Filesystem, log, etc.


Module loader optimized for browser:

Node does not use it.

Why Node.js

The major advantages of Node.js are:

  • There is a huge number of people who know the base language (JavaScript), because every web developer must know JavaScript as it is run on the front-end, while there are tons of backend alternatives (Ruby, Python, PHP, Perl, Java, etc.)

    This means that if you write code in Node.js:

    • many people can understand it already
    • you don't have to learn a new language
  • It is possible to write a single application that runs on:

    • the server
    • the browser
    • locally

    An example application are markdown engines, in which you may want coherent:

    • server backend rendering before giving content to the browser
    • in-browser rendering for preview as you type
    • local rendering for offline development

    It is therefore no surprise that there are currently 3 Node.js markdown engines with huge number of stars on GitHub: Marked, markdown-js and Showdown.


REPL interface:


Run script:

node a.js

Run index.js inside directory:

node dir/

Analogous to require(dir).


The official documentation specifies the stability of each feature.

What each stability level means is specified at:

Level 3 or above guarantee backwards compatibility.

Ubuntu install

Don't install from the official repositories: they are seriously outdated.

Be sane, and use nvm.


Node Version Manager.

Analogous to Ruby RVM or Python virtualenv.

Use it.


curl | sh
# Before using it, you must:
source ~/.nvm/
# so just add that to you `.bashrc`.
echo "source ~/.nvm/
nvm use "$VERSION" &>/dev/null
" >> ~/.bashrc
nvm install "$VERSION"

Install a new version of Node:

nvm install 0.9.0
nvm install 0.9.9

May either download a binary (fast) or compile from source if not possible (slower and requires that you have dev tools installed).

List currently installed node versions:

nvm ls

Use a node version:

nvm use 0.9.9
node --version
nvm use 0.9.0
node --version

Per directory configs:

echo '0.9.9' > .nvmrc

Use per directory config inside .nvmrc:

node use

Always use this in your project root to set the supported node version.

As of early 2014, does not change version automatically like RVM does.


Node package manager. Analogous to Ruby Bundler, Python pip.

As of node 0.9.9 comes together with Node, but several tags behind head.

The config file is package.json.


npm help
npm help install
npm help start


Install all dependencies of package.json in current dir under node_modules:

npm install

Help on the format of package.json:

npm help json

As explained in npm help folders:

  • Local install (default): puts stuff in ./node_modules of the current package root, which is high on the require search path.

    If the module comes with executables, those will be put under ./node_modules/.bin, so you should add the following line to your .bashrc:

    export PATH="./node_modules/.bin:$PATH"

    This way you will use the executables at the same version as specified on the package.json.

  • Global install (with -g): puts stuff in /usr/local or wherever node is installed. TODO: ~/.npm/ vs ~/.nvm/v0.10.26/lib/node_modules/

  • Install it locally if you´re going to require() it.

  • Install it globally if you´re going to run it on the command line.

  • If you need both, then install it in both places, or use npm link.

If the current directory contains a package.json, install given package under ./node_modeules:

npm install package_name

Also modify dependencies of package.json in current directory if there is one to include the new module:

npm install package_name --save

Same for devDependencies:

npm install package_name --saveDev

The main advantage of --save this is that it sets the current version for you: you will probably want to edit the package.json file to put dependencies in alphabetical order.

Versions specification

For dependencies, devDependencies and peerDependencies:

  • caret ^: latest major version. ^1.2.3 matches 1.3.5, but not 2.0.0.

    Default on NPM 1.4.3, and probably a good default, since with semantic versioning it incorporates new features (MINOR) and bug fixes (PATCH).

  • tilde ~: latest minor version. ~1.2.3 matches 1.2.5, but not ~1.2.0

  • "" or "*": any version




npm help scripts

NPM supports a predefined list of scripts to do some common Makefile-like tasks.

Those tasks are either run:

  • when certain npm commands are run, e.g. start or prepublish or postpublish.
  • explicitly through npm run-script <script-name> <package> for any script-name.

You should only use it for scripts that are hooks of things which only NPM can do, e.g., prepublish before node publish. Use the more flexible Grunt for everything else, and preferably redirect all hooks to grunt tasks.

Scripts have default actions, and can be configured through package.json > scripts > name, e.g.:

"scripts": {
  "start": "echo start",
  "test":  "echo test"


Get information on a remote package:

npm info package_name

Returns a JSON which includes information such as available versions and everything inside the package.json.

Useful global packages

npm install -g browserify
npm install -g coffee-script
npm install -g express-generator@3
npm install -g marked


Creates symlinks from projects in any directory into the search path.

Useful for interactive tests of a module inside another project.


cd ~/projects/module1
npm link ../module2

Now, running module1 will use the development version of module2 located at ~/projects/module2 using symlinks.


The following fields are mandatory:

  • name
  • version

Create a package

npm help developers

To be able to require the module as require('module-name'), there must be an index.js in it.

If the main file is not at the base level, e.g. CoffeeScript compiled to dist/index.js, required it from a dummy top level index.js:

module.exports = require('./dist/index')


Every file in the directory is published by npm publish, even if it's not tracked, unless ignored.

If a .npmignore file exists, it lists the ignored files and .gitignore is not used.

package.json and README* are never ignored, even if added to .npmignore.

Otherwise, .gitignore is used.

A .npmignore is necessary in most cases, and it ignores the following files which are normally not gitignored:

  • tests
  • CoffeScript input

To publish a CoffeeScript package:

  • .gititnore the .js output
  • .npmignore the CoffeeScript input
  • prepublish: "grunt coffee"


Short tutorials: