Is there an official style guide or naming convention for React based projects?

Question

I'm setting up a React project with my team that will use mobX as state manager, plus TypeScript.

I've seen a common pattern in the casing and naming patterns in React Projects:

1. Non-React Folders and Files: camelCase or kebab-case
2. React (inside components folder): PascalCase

Is there a formal convention for folder/file naming in react? If not, is there a style guide on which this pattern is based? Or a reason why this one is used most of the times?

Answer 1

Just to add my two cents. As others have stated, file structure is unopinionated. However, component naming is not. They should be PascalCase for React to know whether or not you're using a function, class or an HTMLelement†.

For example:

class input extends Component {...} 

Bad! Why? Because React doesn't know whether or not you're trying to use the input element or the class-based component.

That's why you'll see PascalCase components:

class Input extends Component {...} 

† There is one exception, where you can use dot notation. For example, if you had multiple exports and you import them all as fields, then you could do something like:

component/fields/index.js

import React, { Component } from 'react';  export class input extends Component {   state = { value: "" };    handleChange = ({ target: { value } }) => {     this.setState({ value });   };    render = () => (     <input type="text" value={this.state.value} onChange={this.handleChange} />   ); }  export class textarea extends Component {   state = { value: "" };    handleChange = ({ target: { value } }) => {     this.setState({ value });   };    render = () => (     <textarea       type="text"       value={this.state.value}       onChange={this.handleChange}     />   ); } 

components/App/index.js

import React, { Fragment } from 'react'; import * as fields from "../fields";  const App = () => (   <Fragment>      <fields.input />      <fields.textarea />    <Fragment> );  export default App; 

As a general rule of thumb, I avoid dot notation altogether. It feels clumsy and may confuse other developers who don't know how fields is structured. Plus, I'm not a fan of stacking multiple components within 1 file and then importing them as a bunch. In addition, the file can become quite large and cumbersome to navigate and debug (more on this below).

---

That said, to keep my structure simple, I like to keep main directories lowercase:

├── dist // compiled application files to be served |   ├── css |   |   ├── main.[contenthash:8].css |   |   └── main.[contenthash:8].css.map |   ├── js |   |   ├── main.[hash].js // depending on app size, this may contain multiple js files for code splitting |   |   └── main.[hash].js.map |   ├── media |   |   └── [hash].[ext] // static assets like fonts and images |   └── favicon.ico |   └── index.html | ├── config // supporting "webpackdevserver" configuration files |   ├── devServer.js |   ├── envs.js |   ├── optimization.js |   ├── output.js |   ├── paths.js |   ├── plugins.js |   └── rules.js | ├── public |   ├── favicon.ico |   └── index.html | ├── src |   ├── actions // redux actions |   ├── components // stateful and stateless reusable components that just display "stuff" -- stateful components change and manipulate the UI |   ├── containers // stateful components that utilize the reusable "components" to CRUD data and/or are connected to redux |   ├── images |   ├── pages // utilize components/containers to display something when visiting a "/route" |   ├── reducers // redux reducers |   ├── root // aka "<App />" that combines "routes", redux and other top-level supporting files into one place |   ├── routes // assigns "pages" to a "/route" |   ├── styles // shared and/or global styles used by all "components" |   ├── types // redux types |   ├── utils // supporting app files: like test setup, custom polyfills, axios configurations, ...etc |   └── index.js // a simple file that "ReactDOM.render"s the "App" | ├── server.js // express setup to serve the "dist" folder └── webpack.config.js 

Then within the component folder, I'll PascalCase my components to represent something like this:

└── components     └── Input         ├── __tests__         |   └── Input.test.js // jest unit tests for "index.js"         ├── index.js // all required code/styles to be exported         └── styles.scss // styles required by "index.js" 

Why this structure?

• Reusable components that can be used wherever and whenever.
• Everything that is related to Input is self-contained within this folder. Therefore, I can hand it off to someone and they can slot it in their application and just use it.
• Webpack has been set up to automatically import index.js, so it's very easy to import without traversing a ton of nested files: import Input from 'components/Input'; (also, no need to specify the exact js file to use since "index.js" contains all required code).

Drawbacks:

• You'll have a lot of small folders.
• Compilation errors will all contain the index.js nomenclature so it can be a bit confusing at first as to what "index.js" has failed.

---

Another approach I used to do was:

└── components     ├── input // lowercase name to delineate it's a "pure" function -- the actual function will be a PascalCased "Input"     |   ├── input.test.js // jest unit tests for "input.js"     |   ├── input.js // all required code/styles to be exported     |   └── styles.scss // styles required by "input.js"     |     └── Sidebar // PascalCase because it's a "class"         ├── Sidebar.test.js // jest unit tests for "Sidebar.js"         ├── Sidebar.js // all required code/styles to be exported         └── styles.scss // styles required by "Sidebar.js" 

Why this structure?

• Reusable components that can be used wherever and whenever.
• Everything that is related to Input is self-contained within this folder. Therefore, I can hand it off to someone and they can slot it in their application and just use it.
• Dependent on the main folder, it delineates whether the component is a function or a class.
• When a compilation error occurs, I know exactly which file caused the error.

Drawbacks:

• You'll have a lot of small folders.
• Sometimes a component can change from being stateful to stateless (or vice versa), so if you are strict and stick to this naming pattern, then you'll have to update the main folder to reflect the change, which means you'll also need to update the pathing for any other files that are using this component.
• Imports can look a bit redundant and lengthy: import Input from 'components/input/input.js';

---

Other general guidelines:

• Avoid default exporting an anonymous function:

Example of a default exported anonymous function:

export default () => (   <p>Anonymous Function</p> ); 

Why? Because when testing, the function will show up in enzyme as:

<_default /> 

When you have multiple anonymous functions within a component, which one is which!?

<_default /> <_default /> <_default /> 

• Avoid lengthy files (150 lines or less) as it becomes a pain to read/understand and even more of a pain to debug.

More often than not, I've found that most components will fall under 100 lines or so when properly optimized. Worst case scenario is I'll have to create small subcomponents to supplement the main component. But! Much easier to read and debug.

What's easier to read:

Example #1 (34 lines with supplemental child components)

Example #2 (318 lines of everything)

Example #1 mimics reading a book. Multiple pages that when glued together create an easy-to-read experience. Versus Example #2 which reads a like a mile-long scroll that can be easy to get lost in!

• Stylesheets can be snake-case or camelCase.

This one can be confusing, but it all depends on how you're applying styles. If you're just importing the style like so:

import "./styles.css"; 

Then you can use snake-case:

<input className="snake-case" type="text" value="" onChange={this.handleChange} /> 

However, if you're using css modules, then you'll need to use camelCase:

import { camelCaseClassName } from "./styles.css"; 

Why? Because bundlers (like Webpack) don't support snake-case imports:

<input className={camelCaseClassName} type="text" value="" onChange={this.handleChange} /> 

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Conclusion: There are many ways to create a folder structure with a few tips and tricks to maintain a logical flow. Just pick one that works best for you AND doesn't interfere with the person working beside you!

In other words, K.I.S.S === "Keep it simple, silly!"