Use a linter to enforce code style and prevent common mistakes

Introduction

A linter is a tool that checks your code for style and syntax errors, and can help you enforce a consistent coding style throughout your project. In a React project, you can use a linter like eslint to check your code for mistakes and style issues.

Problem statement

There are several problems that you may face if you do not use a linter in your React projects:

1. Code quality:

Without a linter, you may end up writing code that is difficult to read and understand. This can make it difficult for other developers to work with your code and can lead to maintenance issues in the long run.

function foo(a, b, c) {
  if (a > b) {
    if (a > c) {
      return a
    }
  } else {
    if (b > c) {
      return b
    } else {
      return c
    }
  }
}

A linter can help enforce a consistent coding style, such as using indentation and whitespace, to make the code more readable and easier to understand, like this:

function foo(a, b, c) {
  if (a > b) {
    if (a > c) {
      return a
    }
  } else {
    if (b > c) {
      return b
    } else {
      return c
    }
  }
}

2. Consistency:

A linter helps enforce a consistent coding style across your project. This can make it easier to read and understand code, as well as make it easier for developers to work together on a project.

const user_name = 'John'
const userAge = 30

A linter can help enforce a consistent style, such as requiring all variables to be camelCase, like this:

const userName = 'John'
const userAge = 30

3. Error prevention:

A linter can help catch common mistakes and errors in your code before you even run it. This can save you time and frustration by allowing you to fix errors early on in the development process.

const user = { name: 'John', age: 30 }
console.log(user.name)
console.log(user.age)
console.log(user.email) // This will throw an error because the email property does not exist on the user object

A linter can catch the error on the last line, where the email property is accessed on the user object but does not exist.

4. Improved performance:

A linter can help identify code that may not be optimized for performance, such as code that causes unnecessary re-renders in a React application. This can help you improve the overall performance of your application.

import React, { useState } from 'react'

function Example() {
  const [count, setCount] = useState(0)

  const handleClick = () => {
    setCount(count + 1)
  }

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={handleClick}>Click me</button>
    </div>
  )
}

In this example, the linter might flag the use of count inside the handleClick function as a potential performance issue, because it is not directly passed to the useState hook and may cause unnecessary re-renders. To fix this, you could pass the current value of count to the useState hook like this:

import React, { useState } from 'react';

function Example() {
  const [count, setCount] = useState(0);

  const handleClick = () => {
    setCount(prevCount => prevCount + 1);
  };
  return (
  //other codes
  )
}

Installation

Install the eslint package by following command :

npm install eslint --save-dev

Usage

After installing the package, use the following command :

eslint --init .

This will create an .eslintrc.json file in the root of your project to configure the linter. You can use a popular configuration like the Airbnb style guide, or create your own custom configuration.

{
  "parser": "@typescript-eslint/parser",
  "plugins": ["prefer-arrow-functions", "@typescript-eslint"],
  "extends": ["eslint:recommended", "plugin:react/recommended"],
  "rules": {
    // your custom rules
    // Example rules
    "no-console": "off",
    "no-trailing-spaces": "error",
    "space-in-parens": ["error", "never"],
    "computed-property-spacing": ["error", "never"],
    "indent": "off",
    "@typescript-eslint/indent": ["error", 2],
    "prefer-const": "error",
    "quotes": ["error", "single"],
    "jsx-quotes": ["error", "prefer-single"],
    "semi": ["error", "never"],
    "prefer-arrow-functions/prefer-arrow-functions": "error",
    "react/no-unknown-property": "warn",
    "comma-dangle": ["error", "never"]
  }
}

After configuring the linter, you can run it on your code by running the eslint command in your terminal, followed by the path to the file or directory you want to lint.

eslint . --fix

"scripts": {
  "lint-fix": "eslint . --fix",
},

Once you run the above command you will get suggestions. An example suggestions might look like this :

2:8  warning  'Component' is defined but never used  no-unused-vars

You can also set up your text editor or IDE to display linting errors and warnings as you type, so you can fix mistakes as you go. This can save you time and help you catch errors before you commit your code.

I hope this helps! Let me know if you have any questions.

Example screenshots

Fig : Screenshot after running linter in react project