Nodemon: A tool That Helps Develop Node.js Based Applications

nodemon

nodemon is a tool that helps develop node.js based applications by automatically restarting the node application when file changes in the directory are detected.

nodemon does not require any additional changes to your code or method of development. nodemon is a replacement wrapper for node. To use nodemon, replace the word node on the command line when executing your script.

Installation

Either through cloning with git or by using npm (the recommended way):

npm install -g nodemon

And nodemon will be installed globally to your system path.

You can also install nodemon as a development dependency:

npm install --save-dev nodemon

With a local installation, nodemon will not be available in your system path. Instead, the local installation of nodemon can be run by calling it from within an npm script (such as npm start) or using npx nodemon.

Usage

nodemon wraps your application, so you can pass all the arguments you would normally pass to your app:

nodemon [your node app]

For CLI options, use the -h (or --help) argument:

nodemon -h

Using nodemon is simple, if my application accepted a host and port as the arguments, I would start it as so:

nodemon ./server.js localhost 8080

Any output from this script is prefixed with [nodemon], otherwise all output from your application, errors included, will be echoed out as expected.

You can also pass the inspect flag to node through the command line as you would normally:

nodemon --inspect ./server.js 80

If you have a package.json file for your app, you can omit the main script entirely and nodemon will read the package.json for the main property and use that value as the app (ref).

nodemon will also search for the scripts.start property in package.json (as of nodemon 1.1.x).

Also check out the FAQ or issues for nodemon.

Automatic re-running

nodemon was originally written to restart hanging processes such as web servers, but now supports apps that cleanly exit. If your script exits cleanly, nodemon will continue to monitor the directory (or directories) and restart the script if there are any changes.

Manual restarting

Whilst nodemon is running, if you need to manually restart your application, instead of stopping and restart nodemon, you can type rs with a carriage return, and nodemon will restart your process.

Config files

nodemon supports local and global configuration files. These are usually named nodemon.json and can be located in the current working directory or in your home directory. An alternative local configuration file can be specified with the --config <file> option.

The specificity is as follows, so that a command line argument will always override the config file settings:

• command line arguments
• local config
• global config

A config file can take any of the command line arguments as JSON key values, for example:

{
  "verbose": true,
  "ignore": ["*.test.js", "fixtures/*"],
  "execMap": {
    "rb": "ruby",
    "pde": "processing --sketch={{pwd}} --run"
  }
}

The above nodemon.json file might be my global config so that I have support for ruby files and processing files, and I can run nodemon demo.pde and nodemon will automatically know how to run the script even though out of the box support for processing scripts.

A further example of options can be seen in sample-nodemon.md

package.json

If you want to keep all your package configurations in one place, nodemon supports using package.json for configuration. Specify the config in the same format as you would for a config file but under nodemonConfig in the package.json file, for example, take the following package.json:

{
  "name": "nodemon",
  "homepage": "http://nodemon.io",
  "...": "... other standard package.json values",
  "nodemonConfig": {
    "ignore": ["test/*", "docs/*"],
    "delay": 2500
  }
}

Note that if you specify a --config file or provide a local nodemon.json any package.json config is ignored.

This section needs better documentation, but for now you can also see nodemon --help config (also here).

Using nodemon as a module

Please see doc/requireable.md

Using nodemon as child process

Please see doc/events.md

Running non-node scripts

nodemon can also be used to execute and monitor other programs. nodemon will read the file extension of the script being run and monitor that extension instead of .js if there's no nodemon.json:

nodemon --exec "python -v" ./app.py

Now nodemon will run app.py with python in verbose mode (note that if you're not passing args to the exec program, you don't need the quotes), and look for new or modified files with the .py extension.

Default executables

Using the nodemon.json config file, you can define your own default executables using the execMap property. This is particularly useful if you're working with a language that isn't supported by default by nodemon.

To add support for nodemon to know about the .pl extension (for Perl), the nodemon.json file would add:

{
  "execMap": {
    "pl": "perl"
  }
}

Now running the following, nodemon will know to use perl as the executable:

nodemon script.pl

It's generally recommended to use the global nodemon.json to add your own execMap options. However, if there's a common default that's missing, this can be merged in to the project so that nodemon supports it by default, by changing default.js and sending a pull request.

Monitoring multiple directories

By default nodemon monitors the current working directory. If you want to take control of that option, use the --watch option to add specific paths:

nodemon --watch app --watch libs app/server.js

Now nodemon will only restart if there are changes in the ./app or ./libs directory. By default nodemon will traverse sub-directories, so there's no need in explicitly including sub-directories.

Don't use unix globbing to pass multiple directories, e.g --watch ./lib/*, it won't work. You need a --watch flag per directory watched.

Specifying extension watch list

By default, nodemon looks for files with the .js, .mjs, .coffee, .litcoffee, and .json extensions. If you use the --exec option and monitor app.py nodemon will monitor files with the extension of .py. However, you can specify your own list with the -e (or --ext) switch like so:

nodemon -e js,pug

Now nodemon will restart on any changes to files in the directory (or subdirectories) with the extensions .js, .pug.

Ignoring files

By default, nodemon will only restart when a .js JavaScript file changes. In some cases you will want to ignore some specific files, directories or file patterns, to prevent nodemon from prematurely restarting your application.

This can be done via the command line:

nodemon --ignore lib/ --ignore tests/

Or specific files can be ignored:

nodemon --ignore lib/app.js

Patterns can also be ignored (but be sure to quote the arguments):

nodemon --ignore 'lib/*.js'

Note that by default, nodemon will ignore the .git, node_modules, bower_components, .nyc_output, coverage and .sass-cache directories and add your ignored patterns to the list. If you want to indeed watch a directory like node_modules, you need to override the underlying default ignore rules.

Application isn't restarting

In some networked environments (such as a container running nodemon reading across a mounted drive), you will need to use the legacyWatch: true which enables Chokidar's polling.

Via the CLI, use either --legacy-watch or -L for short:

nodemon -L

Though this should be a last resort as it will poll every file it can find.

Delaying restarting

In some situations, you may want to wait until a number of files have changed. The timeout before checking for new file changes is 1 second. If you're uploading a number of files and it's taking some number of seconds, this could cause your app to restart multiple times unnecessarily.

To add an extra throttle, or delay restarting, use the --delay command:

nodemon --delay 10 server.js

For more precision, milliseconds can be specified. Either as a float:

nodemon --delay 2.5 server.js

Or using the time specifier (ms):

nodemon --delay 2500ms server.js

The delay figure is number of seconds (or milliseconds, if specified) to delay before restarting. So nodemon will only restart your app the given number of seconds after the last file change.

If you are setting this value in nodemon.json, the value will always be interpreted in milliseconds. E.g., the following are equivalent:

nodemon --delay 2.5

{
  "delay": 2500
}

Gracefully reloading down your script

It is possible to have nodemon send any signal that you specify to your application.

nodemon --signal SIGHUP server.js

Your application can handle the signal as follows.

process.once("SIGHUP", function () {
  reloadSomeConfiguration();
})

Please note that nodemon will send this signal to every process in the process tree.

If you are using cluster, then each workers (as well as the master) will receive the signal. If you wish to terminate all workers on receiving a SIGHUP, a common pattern is to catch the SIGHUP in the master, and forward SIGTERM to all workers, while ensuring that all workers ignore SIGHUP.

if (cluster.isMaster) {
  process.on("SIGHUP", function () {
    for (const worker of Object.values(cluster.workers)) {
      worker.process.kill("SIGTERM");
    }
  });
} else {
  process.on("SIGHUP", function() {})
}

Controlling shutdown of your script

nodemon sends a kill signal to your application when it sees a file update. If you need to clean up on shutdown inside your script you can capture the kill signal and handle it yourself.

The following example will listen once for the SIGUSR2 signal (used by nodemon to restart), run the clean up process and then kill itself for nodemon to continue control:

process.once('SIGUSR2', function () {
  gracefulShutdown(function () {
    process.kill(process.pid, 'SIGUSR2');
  });
});

Note that the process.kill is only called once your shutdown jobs are complete. Hat tip to Benjie Gillam for writing this technique up.

Triggering events when nodemon state changes

If you want growl like notifications when nodemon restarts or to trigger an action when an event happens, then you can either require nodemon or add event actions to your nodemon.json file.

For example, to trigger a notification on a Mac when nodemon restarts, nodemon.json looks like this:

{
  "events": {
    "restart": "osascript -e 'display notification \"app restarted\" with title \"nodemon\"'"
  }
}

A full list of available events is listed on the event states wiki. Note that you can bind to both states and messages.

Pipe output to somewhere else

nodemon({
  script: ...,
  stdout: false // important: this tells nodemon not to output to console
}).on('readable', function() { // the `readable` event indicates that data is ready to pick up
  this.stdout.pipe(fs.createWriteStream('output.txt'));
  this.stderr.pipe(fs.createWriteStream('err.txt'));
});

Using nodemon in your gulp workflow

Check out the gulp-nodemon plugin to integrate nodemon with the rest of your project's gulp workflow.

Using nodemon in your Grunt workflow

Check out the grunt-nodemon plugin to integrate nodemon with the rest of your project's grunt workflow.

Pronunciation

nodemon, is it pronounced: node-mon, no-demon or node-e-mon (like pokémon)?

Well...I've been asked this many times before. I like that I've been asked this before. There's been bets as to which one it actually is.

The answer is simple, but possibly frustrating. I'm not saying (how I pronounce it). It's up to you to call it as you like. All answers are correct :)

Design principles

• Fewer flags is better
• Works across all platforms
• Fewer features
• Let individuals build on top of nodemon
• Offer all CLI functionality as an API
• Contributions must have and pass tests

Nodemon is not perfect, and CLI arguments has sprawled beyond where I'm completely happy, but perhaps it can be reduced a little one day.

FAQ

See the FAQ and please add your own questions if you think they would help others.

Author: Remy
Source Code: https://github.com/remy/nodemon 
License: MIT License

#node #hacktoberfest 

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Why use Node.js for Web Development? Benefits and Examples of Apps

Front-end web development has been overwhelmed by JavaScript highlights for quite a long time. Google, Facebook, Wikipedia, and most of all online pages use JS for customer side activities. As of late, it additionally made a shift to cross-platform mobile development as a main technology in React Native, Nativescript, Apache Cordova, and other crossover devices. 

Throughout the most recent couple of years, Node.js moved to backend development as well. Designers need to utilize a similar tech stack for the whole web project without learning another language for server-side development. Node.js is a device that adjusts JS usefulness and syntax to the backend. 

What is Node.js? 

Node.js isn’t a language, or library, or system. It’s a runtime situation: commonly JavaScript needs a program to work, however Node.js makes appropriate settings for JS to run outside of the program. It’s based on a JavaScript V8 motor that can run in Chrome, different programs, or independently. 

The extent of V8 is to change JS program situated code into machine code — so JS turns into a broadly useful language and can be perceived by servers. This is one of the advantages of utilizing Node.js in web application development: it expands the usefulness of JavaScript, permitting designers to coordinate the language with APIs, different languages, and outside libraries.

What Are the Advantages of Node.js Web Application Development? 

Of late, organizations have been effectively changing from their backend tech stacks to Node.js. LinkedIn picked Node.js over Ruby on Rails since it took care of expanding responsibility better and decreased the quantity of servers by multiple times. PayPal and Netflix did something comparative, just they had a goal to change their design to microservices. We should investigate the motivations to pick Node.JS for web application development and when we are planning to hire node js developers. 

Amazing Tech Stack for Web Development 

The principal thing that makes Node.js a go-to environment for web development is its JavaScript legacy. It’s the most well known language right now with a great many free devices and a functioning local area. Node.js, because of its association with JS, immediately rose in ubiquity — presently it has in excess of 368 million downloads and a great many free tools in the bundle module. 

Alongside prevalence, Node.js additionally acquired the fundamental JS benefits: 

• quick execution and information preparing; 
• exceptionally reusable code; 
• the code is not difficult to learn, compose, read, and keep up; 
• tremendous asset library, a huge number of free aides, and a functioning local area. 

In addition, it’s a piece of a well known MEAN tech stack (the blend of MongoDB, Express.js, Angular, and Node.js — four tools that handle all vital parts of web application development). 

Designers Can Utilize JavaScript for the Whole Undertaking 

This is perhaps the most clear advantage of Node.js web application development. JavaScript is an unquestionable requirement for web development. Regardless of whether you construct a multi-page or single-page application, you need to know JS well. On the off chance that you are now OK with JavaScript, learning Node.js won’t be an issue. Grammar, fundamental usefulness, primary standards — every one of these things are comparable. 

In the event that you have JS designers in your group, it will be simpler for them to learn JS-based Node than a totally new dialect. What’s more, the front-end and back-end codebase will be basically the same, simple to peruse, and keep up — in light of the fact that they are both JS-based. 

A Quick Environment for Microservice Development 

There’s another motivation behind why Node.js got famous so rapidly. The environment suits well the idea of microservice development (spilling stone monument usefulness into handfuls or many more modest administrations). 

Microservices need to speak with one another rapidly — and Node.js is probably the quickest device in information handling. Among the fundamental Node.js benefits for programming development are its non-obstructing algorithms.

Node.js measures a few demands all at once without trusting that the first will be concluded. Many microservices can send messages to one another, and they will be gotten and addressed all the while. 

Versatile Web Application Development 

Node.js was worked in view of adaptability — its name really says it. The environment permits numerous hubs to run all the while and speak with one another. Here’s the reason Node.js adaptability is better than other web backend development arrangements. 

Node.js has a module that is liable for load adjusting for each running CPU center. This is one of numerous Node.js module benefits: you can run various hubs all at once, and the environment will naturally adjust the responsibility. 

Node.js permits even apportioning: you can part your application into various situations. You show various forms of the application to different clients, in light of their age, interests, area, language, and so on. This builds personalization and diminishes responsibility. Hub accomplishes this with kid measures — tasks that rapidly speak with one another and share a similar root. 

What’s more, Node’s non-hindering solicitation handling framework adds to fast, letting applications measure a great many solicitations. 

Control Stream Highlights

Numerous designers consider nonconcurrent to be one of the two impediments and benefits of Node.js web application development. In Node, at whatever point the capacity is executed, the code consequently sends a callback. As the quantity of capacities develops, so does the number of callbacks — and you end up in a circumstance known as the callback damnation. 

In any case, Node.js offers an exit plan. You can utilize systems that will plan capacities and sort through callbacks. Systems will associate comparable capacities consequently — so you can track down an essential component via search or in an envelope. At that point, there’s no compelling reason to look through callbacks.

 

Final Words

So, these are some of the top benefits of Nodejs in web application development. This is how Nodejs is contributing a lot to the field of web application development. 

I hope now you are totally aware of the whole process of how Nodejs is really important for your web project. If you are looking to hire a node js development company in India then I would suggest that you take a little consultancy too whenever you call. 

Good Luck!

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I believe this list will help you out in choosing the best NodeJS service provider company. So, now let’s explore the top NodeJS developer companies to choose from in 2021.

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