Tips, tricks and tools for debugging a Node.js Application

Software development is complex and, at some point, your Node.js application will fail. If you’re lucky, your code will crash with an obvious error message. If you’re unlucky, your application will carry on regardless but not generate the results you expect. If you’re really unlucky, everything will work fine until the first user discovers a catastrophic disk-wiping bug.

What is Debugging?

Debugging is the black art of fixing software defects. Fixing a bug is often easy — a corrected character or additional line of code solves the problem. Finding that bug is another matter, and developers can spend many unhappy hours trying to locate the source of an issue. Fortunately, Node.js has some great tools to help trace errors.

Terminology

Debugging has its own selection of obscure jargon, including the following:

How to Avoid Bugs

Bugs can often be prevented before you test your application …

Use a Good Code Editor

A good code editor will offer numerous features including line numbering, auto-completion, color-coding, bracket matching, formatting, auto-indentation, variable renaming, snippet reuse, object inspection, function navigation, parameter prompts, refactoring, unreachable code detection, suggestions, type checking, and more.

Node.js devs are spoiled for choice with free editors such as VS Code, Atom, and Brackets, as well as plenty of commercial alternatives.

Use a Code Linter

A linter can report code faults such as syntax errors, poor indentation, undeclared variables, and mismatching brackets before you save and test your code. The popular options for JavaScript and Node.js include ESLint, JSLint, and JSHint.

These are often installed as global Node.js modules so you can run checks from the command line:

eslint myfile.js

However, most linters have code editor plugins, such as ESLint for VS Code and linter-eslint for Atom which check your code as you type:

Use Source Control

A source control system such as Git can help safe-guard your code and manage revisions. It becomes easier to discover where and when a bug was introduced and who should receive the blame! Online repositories such as GitHub and Bitbucket offer free space and management tools.

Adopt an Issue-tracking System

Does a bug exist if no one knows about it? An issue-tracking system is used to report bugs, find duplicates, document reproduction steps, determine severity, calculate priorities, assign developers, record discussions, and track progress of any fixes.

Online source repositories often offer basic issue tracking, but dedicated solutions may be appropriate for larger teams and projects.

Use Test-driven Development

Test-driven Development (TDD) is a development process which encourages developers to write code which tests the operation of a function before it’s written — for example, is X returned when function Y is passed input Z.

Tests can be run as the code is developed to prove a function works and spot any issues as further changes are made. That said, your tests could have bugs too …

Step Away

It’s tempting to stay up all night in a futile attempt to locate the source of a nasty bug. Don’t. Step away and do something else. Your brain will subconsciously work on the problem and wake you at 4am with a solution. Even if that doesn’t happen, fresh eyes will spot that obvious missing semicolon.

Node.js Debugging: Environment Variables

Environment variables that are set within the host operating system can be used to control Node.js application settings. The most common is NODE_ENV, which is typically set to development when debugging.

Environment variables can be set on Linux/macOS:

NODE_ENV=development

Windows cmd:

set NODE_ENV=development

Or Windows Powershell:

$env:NODE_ENV="development"

Internally, an application will enable further debugging features and messages. For example:

// is NODE_ENV set to "development"?
const DEVMODE = (process.env.NODE_ENV === 'development');

if (DEVMODE) {
  console.log('application started in development mode on port ${PORT}');
}

NODE_DEBUG enables debugging messages using the Node.js util.debuglog (see below), but also consult the documentation of your primary modules and frameworks to discover further options.

Note that environment variables can also be saved to a .env file. For example:

NODE_ENV=development
NODE_LOG=./log/debug.log
SERVER_PORT=3000
DB_HOST=localhost
DB_NAME=mydatabase

Then loaded using the dotenv module:

require('dotenv').config();

Node.js Debugging: Command Line Options

Various command-line options can be passed to the node runtime when launching an application. One of the most useful is --trace-warnings, which outputs stack traces for process warnings (including deprecations).

Any number of options can be set, including:

• --enable-source-maps: enable source maps (experimental)
• --throw-deprecation: throw errors when deprecated features are used
• --inspect: activate the V8 inspector (see below)

By way of an example, let’s try to log the crypto module’s DEFAULT_ENCODING property, which was deprecated in Node v10:

const crypto = require('crypto');

function bar() {
  console.log(crypto.DEFAULT_ENCODING);
}

function foo(){
  bar();
}

foo();

Now run this with the following:

node index.js

We’ll then see this:

buffer
(node:7405) [DEP0091] DeprecationWarning: crypto.DEFAULT_ENCODING is deprecated.

However, we can also do this:

node --trace-warnings index.js

That produces the following:

buffer
(node:7502) [DEP0091] DeprecationWarning: crypto.DEFAULT_ENCODING is deprecated.
    at bar (/home/Desktop/index.js:4:22)
    at foo (/home/Desktop/index.js:8:3)
    at Object.<anonymous> (/home/Desktop/index.js:11:1)
    at Module._compile (internal/modules/cjs/loader.js:1151:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1171:10)
    at Module.load (internal/modules/cjs/loader.js:1000:32)
    at Function.Module._load (internal/modules/cjs/loader.js:899:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
    at internal/main/run_main_module.js:17:47

This tells us that the deprecation warning comes from the code in line 4 (the console.log statement), which was executed when the bar function ran. The bar function was called by the foo function on line 8 and the foo function was called on line 11 of our script.

Note that the same options can also be passed to nodemon.

Console Debugging

One of the easiest ways to debug an application is to output values to the console during execution:

console.log( myVariable );

Few developers delve beyond this humble debugging command, but they’re missing out on many more possibilities, including these:

console.log() accepts a list of comma-separated values. For example:

let x = 123;
console.log('x:', x);
// x: 123

However, ES6 destructuring can offer similar output with less typing effort:

console.log({x});
// { x: 123 }

Larger objects can be output as a condensed string using this:

console.log( JSON.stringify(obj) );

util.inspect will format objects for easier reading, but console.dir() does the hard work for you.

Node.js util.debuglog

The Node.js util module offers a built-in debuglog method which conditionally writes messages to STDERR:

const util = require('util');
const debuglog = util.debuglog('myapp');

debuglog('myapp debug message [%d]', 123);

When the NODE_DEBUG environment variable is set to myapp (or a wildcard such as * or my*), messages are displayed in the console:

NODE_DEBUG=myapp node index.js
MYAPP 9876: myapp debug message [123]

Here, 9876 is the Node.js process ID.

By default, util.debuglog is silent. If you were to run the above script without setting a NODE_DEBUG variable, nothing would be output to the console. This allows you to leave helpful debug logging in your code without cluttering the console for regular use.

Debugging with Log Modules

Third-party logging modules are available should you require more sophisticated options for messaging levels, verbosity, sorting, file output, profiling, and more. Popular options include:

• cabin
• loglevel
• morgan (Express.js middleware)
• pino
• signale
• storyboard
• tracer
• winston

Node.js V8 Inspector

git clone https://github.com/sitepoint-editors/pagehit-ram

Or you can use any of your own code.

Node.js is a wrapper around the V8 JavaScript engine which includes its own inspector and debugging client. To start, use the inspect argument (not to be confused with --inspect) to start an application:

node inspect ./index.js

The debugger will pause at the first line and display a debug> prompt:

< Debugger listening on ws://127.0.0.1:9229/6f38abc1-8568-4035-a5d2-dee6cbbf7e44
< For help, see: https://nodejs.org/en/docs/inspector
< Debugger attached.
Break on start in index.js:7
  5 const
  6   // default HTTP port
> 7   port = 3000,
  8
  9   // Node.js modules
debug>

You can step through the application by entering:

• cont or c: continue execution
• next or n: run the next command
• step or s: step into a function being called
• out or o: step out of a function and return to the calling command
• pause: pause running code

Other options include:

• watching variable values with watch('myvar')
• setting breakpoints with the setBreakpoint()/sb() command (it is usually easier to insert a debugger; statement in your code)
• restart a script
• .exit the debugger (the initial . is required)

If this sounds horribly clunky, it is. Only use the built-in debugging client when there’s absolutely no other option, you’re feeling particularly masochistic, and you’re not using Windows (it’s often problematic).

Node.js Debugging with Chrome

The Node.js inspector (without the debugger client) is started with the --inspect flag:

node --inspect ./index.js

Note: nodemon can be used instead of node if necessary.

This starts the debugger listening on 127.0.0.1:9229, which any local debugging client can attach to:

Debugger listening on ws://127.0.0.1:9229/20ac75ae-90c5-4db6-af6b-d9d74592572f

If you’re running the Node.js application on another device or Docker container, ensure port 9229 is accessible and grant remote access using this:

node --inspect=0.0.0.0:9229 ./index.js

Alternatively, you can use --inspect-brk to set a breakpoint on the first statement so the application is paused immediately.

Open Chrome and enter chrome://inspect in the address bar.

Note: if the Node.js application does’t appear as a Remote Target, ensure Discover network targets is checked, then click Configure to add the IP address and port of the device where the application is running.

Click the Target’s inspect link to launch DevTools. It will be immediately familiar to anyone with browser debugging experience.

The + Add folder to workspace link allows you to select where the Node.js files are located on your system, so it becomes easier to load other modules and make changes.

Clicking any line number sets a breakpoint, denoted by a green marker, which stops execution when that code is reached:

Variables can be added to the Watch pane on the right by clicking the + icon and entering their name. Their value is shown whenever execution is paused.

The Call Stack pane shows which functions were called to reach this point.

The Scope pane shows the state of all available local and global variables.

The Breakpoints pane shows a list of all breakpoints and allows them to be enabled or disabled.

The icons above the Debugger paused message can be used to resume execution, step over, step into, step out, step through, deactivate all breakpoints, and pause on exceptions.

Node.js Debugging with VS Code

VS Code Node.js debugging can be launched without any configuration when you’re running a Node.js application on your local system. Open the starting file (typically index.js), activate the Run and Debug pane, and click the Run and Debug Node.js (F5) button.

The debugging screen is similar to Chrome DevTools with a Variables, Watch, Call stack, Loaded scripts, and Breakpoints list.

A breakpoint can be set by clicking the gutter next to the line number. You can also right-click.

With this right-click, you can set the following:

1. A standard breakpoint.

2. A conditional breakpoint which stops when criteria are met — for example, count > 3.

3. A logpoint, which is effectively console.log() without code! Any string can be entered with expressions denoted in curly braces — for example, {count} to display the value of the count variable.

Note: don’t forget to hit Return for VS Code to create your conditional breakpoint or logpoint.

The debugging icon bar at the top can be used to resume execution, step over, step into, step out, restart, or stop the application and debugging. Identical options are also available from the Debug item in the menu.

For more information, refer to Debugging in Visual Studio Code.

Advanced Debugging Configuration

Further configuration is required when you’re debugging a remote service or need to use different launch options. VS Code stores launch configurations in a launch.json file generated inside the .vscode folder within your project. To generate or edit the file, click the cog icon at the top right of the Run and Debug pane.

Any number of configuration settings can be added to the configurations array. Click the Add Configuration button to choose an option. VS Code can either:

1. launch a process using Node.js itself, or
2. attach to a Node.js inspector process, perhaps running on a remote machine or Docker container

In the example above, a single Nodemon launch configuration has been defined. Save launch.json, select nodemon from the drop-down list at the top of the Run and Debug pane, and click the green start icon.

For further information, see VS Code Launch configurations.

Other Node.js Debugging Tools

The Node.js Debugging Guide provides advice for other IDEs and editors including Visual Studio, JetBrains, WebStorm, Gitpod, and Eclipse. Atom also has a node-debug extension.

ndb offers an improved debugging experience with powerful features such as attaching to child processes and script blackboxing so only code in specific folders is shown.

The IBM report-toolkit for Node.js works by analyzing data output when node is run with the --experimental-report option.

Get Debugging!

Node.js has a range of great debugging tools and code analyzers which can improve the speed and reliability of your application. Whether or not they can tempt you away from console.log() is another matter!

#nodejs #javascript #web-development #node-js

What is GEEK

Buddha Community

top 30 Python Tips and Tricks for Beginners

Welcome to my Blog , In this article, you are going to learn the top 10 python tips and tricks.

1) swap two numbers.

2) Reversing a string in Python.

3) Create a single string from all the elements in list.

4) Chaining Of Comparison Operators.

5) Print The File Path Of Imported Modules.

6) Return Multiple Values From Functions.

7) Find The Most Frequent Value In A List.

8) Check The Memory Usage Of An Object.

…

#python #python hacks tricks #python learning tips #python programming tricks #python tips #python tips and tricks #python tips and tricks advanced #python tips and tricks for beginners #python tips tricks and techniques #python tutorial #tips and tricks in python #tips to learn python #top 30 python tips and tricks for beginners

Node JS Development Company| Node JS Web Developers-SISGAIN

Top organizations and start-ups hire Node.js developers from SISGAIN for their strategic software development projects in Illinois, USA. On the off chance that you are searching for a first rate innovation to assemble a constant Node.js web application development or a module, Node.js applications are the most appropriate alternative to pick. As Leading Node.js development company, we leverage our profound information on its segments and convey solutions that bring noteworthy business results. For more information email us at hello@sisgain.com

#node.js development services #hire node.js developers #node.js web application development #node.js development company #node js application

Hire Dedicated Node.js Developers - Hire Node.js Developers

If you look at the backend technology used by today’s most popular apps there is one thing you would find common among them and that is the use of NodeJS Framework. Yes, the NodeJS framework is that effective and successful.

If you wish to have a strong backend for efficient app performance then have NodeJS at the backend.

WebClues Infotech offers different levels of experienced and expert professionals for your app development needs. So hire a dedicated NodeJS developer from WebClues Infotech with your experience requirement and expertise.

So what are you waiting for? Get your app developed with strong performance parameters from WebClues Infotech

For inquiry click here: https://www.webcluesinfotech.com/hire-nodejs-developer/

Book Free Interview: https://bit.ly/3dDShFg

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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!

Original Source

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Top 10 NodeJs app Development Companies- ValueCoders

Node.js is a prominent tech trend in the space of web and mobile application development. It has been proven very efficient and useful for a variety of application development. Thus, all business owners are eager to leverage this technology for creating their applications.

Are you striving to develop an application using Node.js? But can’t decide which company to hire for NodeJS app development? Well! Don’t stress over it, as the following list of NodeJS app development companies is going to help you find the best partner.

Let’s take a glance at top NodeJS application development companies to hire developers in 2021 for developing a mind-blowing application solution.

Before enlisting companies, I would like to say that every company has a foundation on which they thrive. Their end goals, qualities, and excellence define their competence. Thus, I prepared this list by considering a number of aspects. While making this list, I have considered the following aspects:

• Review and rating
• Enlisted by software peer & forums
• Hourly price
• Offered services
• Year of experience (Average 8+ years)
• Credibility & Excellence
• Served clients and more

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.

#1. JSGuru

JSGuru is a top-rated NodeJS app development company with an innovative team of dedicated NodeJS developers engaged in catering best-class UI/UX design, software products, and AWS professional services.

It is a team of one of the most talented developers to hire for all types of innovative solution development, including social media, dating, enterprise, and business-oriented solutions. The company has worked for years with a number of startups and launched a variety of products by collaborating with big-name corporations like T-systems.

If you want to hire NodeJS developers to secure an outstanding application, I would definitely suggest them. They serve in the area of eLearning, FinTech, eCommerce, Telecommunications, Mobile Device Management, and more.

• Ratings: 4.9/5.0

• Founded: 2006

• Headquarters: Banja Luka, Bosnia, and Herzegovina

• Price: Starting from $50/hour

Visit Website - https://www.valuecoders.com/blog/technology-and-apps/top-node-js-app-development-companies

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