Node

REPL

You can start the node REPL by using the node command in the terminal.

$ node

npm

To create a new package.json file use init command.

$ npm init

You can install dependencies specified in package.json by using the install command.

$ npm install some-package-name

You can install multiple dependencies with a single install command by separating each dependency name with a space.

$ npm install some-package-name another-package and-another-one

You can abbreviate the install command to i. You can use this in place of install on any command.

$ npm i some-package-name

To install a dependency as a development dependency only use the --save-dev flag.

$ npm install --save-dev some-dev-dependency-name

Package

The package.json file contains a range of dependencies and descriptors for your project.

You can add a list of development dependencies using the devDependencies key.

{
  "devDependencies": {
    "some-dependency": "*",
  }
}

Link

You can link a project’s dependencies to a locally developed resource by using the npm link command. This utility is useful if you are working on a project that has a dependency on a resource that you also develop and are modifying, by linking your project’s dependency to the locally developed version you can update the dependency and see those changes reflected immediately in your project.

You can activate npm link by navigating to the source folder for your package that acts as a dependency and executing the npm link command to create a global link to that package, then navigating to the project that uses that dependency and calling npm link <DEPENDENCY FOLDER NAME> to set up a link. In the example below, linked folders are indicated with a ~.

projects
├── my-app
|   └── node_modules
|       └── my_dependency_project ~
└── my_dependency_project ~

For the file structure above you would run the following commands.

$ cd projects/my_dependency_project
$ npm link # set up global symlink
$ cd ../my-app
$ npm link my_dependency_project

You can remove links with the npm unlink command.

$ npm unlink

npx

The npx command temporarily downloads a package and runs it.

$ npx cowsay I AM COW

fs

You can delete a file from a directory using the unlink method (an asynchronous deletion method) or the unlinkSync method (the synchronous version of the same functionality), simply pass the file of the path you want to delete as an argument. The async version also takes a callback that runs when the deletion finishes.

var path = './path/to/file.txt'
fs.unlinkSync(path); // delete file synchronously

fs.unlink(path, (err) => { // delete file asynchronously
  // do something when file is deleted
});

You can copy a file from one directory to another using the createReadStream and createWriteStream functions with a pipe. This is useful as it allows you to be agnostic about the content you are copying. For example, if you had to read the content into the programs memory in an opinionated way, things like images, text, audio etc. would need special configurations to avoid corruption, so, by simply reading the files in as a stream of data and piping that stream directly to an output file, nothing is altered in any way and this gives you a very easy way to copy files between two locations using node.

const fs = require('fs');
fs.createReadStream('source_file.ext').pipe(fs.createWriteStream('target_file.ext'));

Process

You can make your node application exit by using the .exit method on the process object.

process.exit();

Frameworks

Handlebars

Handlebars is an extension for Express that allows you to pass content dynamically from your server to your web pages and set up web pages which injected reproducible code into multiple web pages.. The directory for Handlebars to work should be structured like so:

.
├── app.js
└── views
    ├── home.handlebars
    └── layouts
        └── main.handlebars

Where views/layouts/main.handlebars represents code that will appear on each page, and layouts/main.handlebars represents a page in our website. To insert the content from a page into a handlebars layout use the } indicator. In the below example the content from a specific page will be inserted where into a <div> with class="my div" for every page on our website.

<div class="my div">
  }
</div>

To create a route to your main.handlebars page use express’s routing function, which has '/' representing the root url.

app.get('/', function (req, res) {
  res.render('home')
});

You can variables to your web pages from your server using the app.get() function and adding input variable dictionaries as an argument to the render() function.

app.get('/', function (req, res) {
  res.render('home', {
    stuff: "Stuff variable"
  });
});

This can then be referenced from your HTML page using `` braces which will inject that variables content into these html tags.

<p></p>

You can pass in variables to this dictionary as well to render logical parts of your code.

const other_stuff = "Other stuff variable";
// pass the variable in
app.get('/', function (req, res) {
  res.render('home', {
    stuff: other_stuff
  });
});

Nodemon

By default you must restart you node server every time you make a change to your serve code so that it can run. Nodemon is an automated service that monitors your node server and restarts it automatically when server code changes are made.

You can install Nodemon using npm install -D nodemon. The -D indicates that this install is for development purposes only and shouldn’t be included with a release version of our node app.

You can trigger nodemon server running by adding a new script the package.json file that runs nodemon on whatever your root file is.

"scripts": {
  "dev": "nodemon SERVER_FILE_NAME"
}

You can then trigger this nodemon script with the command npm run dev. You can also give this script whatever name you want, like tomato.

Karma

The Karma framework allows you to run browser based javascript tests, like Jasmine, from the command line.

You can specify the type of reporting you get by changes the reporters section of the karma.conf.js file. You will often need to add and npm install these reporters as dependencies as well.

reporters: ['progress', 'spec', 'super-dots']

Browserify

Browserify allows you to bundle code written in node with many dependencies into a single bundle.js file that will run in the browser. After having written your node code, with standard requires and classes etc. Create a top level script (such as main.js) that calls the dependencies you have created to do something. This is the file you should target with Browserify which will take this file, scope out all its dependencies, and return a single bundle.js file that will run all the code. To install Browserify use:

$ npm install uniq

To then bundle your javascript into a single file use:

$ browserify main.js -o bundle.js

After this, all you need to do is require the bundle.js on a page as a script.