# Linter in Node App: Manage Code Quality


You can get the final source code from here.

## Linter

A linter tool analyzes code and warns for potential errors. Also, force to maintain a generic style and structure.

For example, when an application has multiple contributors, it is important to follow the same coding style. In this situation, Linter tools come quite handy.

[Airbnb](https://github.com/airbnb/javascript) has an industry standard style guide and we are going to implement it.

## Tools

To use the linter tool in node application, we are going to use,

* Visual Studio Code (code editor)

* [eslint](https://www.npmjs.com/package/eslint) (npm package)

* [eslint-plugin-import](https://www.npmjs.com/package/eslint-plugin-import) (npm package)

* [eslint-config-airbnb-base](https://www.npmjs.com/package/eslint-config-airbnb-base) (npm package)

* [ESLint](https://marketplace.visualstudio.com/items?itemName=dbaeumer.vscode-eslint) (editor extension)

## Light, Camera, Action

1. Install the editor for your suitable platform

1. Install [Node.js](https://medium.com/@bmshamsnahid/node-101-install-and-get-started-with-node-js-8442dea963a4) in your machine

1. Make sure both `node` and `npm` is installed in your system

1. Open **Visual Studio Code **and install the **ESLint** extension.

To install **ESLint **extension in **Visual Studio Code**

* Open the code editor

* Open vs code extension panel (Crtl+Shift+X)

* Search for **ESLint**

* Install the extension

## Prepare Project

Create a directory, `linterPractice` and enter the directory.

```
mkdir linterPractice

cd linterPractice
```


Now in the root directory, create the project

```
npm init -y
```


Now open the directory in your code editor.

Create two files named `index.js` and `.eslintrc.js`

Your project directory should look like

```
├── ...
├── manageEnvironment                        
│   ├── index.js
│   ├── .eslintrc.js             
│   └── package.json
├── ...
```


Install the npm packages from the root directory.

```
npm i -D eslint eslint-config-airbnb-base eslint-plugin-import
```


Now add linter configuration to `.eslintrc.js` file

```
module.exports = {
  "extends": "airbnb-base",
  "rules": {}
};
```


## Usage

Now you are done setting linter tool in your node application. Let’s see some special use case of linter.

### Override Linter Rule

To override some rule, update your `.eslintrc.js` in `rules` section.

By default, linter does not allow `under-score`. So to use `uder-score` we have to override the rule and updated `configuration` will be

```
module.exports = {
  "extends": "airbnb-base",
  "rules": {
    "no-underscore-dangle": 0
  }
};
```


### Ignore Linter Rule InSpecific File

By default, `eslint` does not support linting. To override a rule in a specific file, we can comment to override the rule. In the following code blocks, I will override `console` rule in `index.js` file.

```
/* eslint-disable no-console */

console.log(‘Hello world’);
```


## Final Word

Stay tuned and if there is a confusing term or something, the response below. I will replay ASAP.