During the software development proccess is important keeping the code well organized and readable, following a development quality standard that will facilitate future maintenance. However, performing this formatting manually or even having to standardize old code can be tedious.

Thus, this article aims to present the configuration of a React.js project with typescript using eslint and prettir to standardize the source code.

Project creation

• yarn create react-app todo_list

At the root of the project:

Typescript dependencies

• yarn add typescript @types/node @types/react @types/react-dom @types/jest -D

ESlint and prettier installation

• The eslint package will inform us when some code is not following the development pattern.

• The prettier package will aplly the pattern.

• yarn add eslint prettier eslint-config-prettier eslint-plugin-prettier -D

After installations, run: yarn eslint --init and following the steps:

1. To check syntax, find problems, and enforce code style
2. JavaScript modules (import/export)
3. React
4. Does your project use TypeScript? y
5. Browser
6. Use a popular style guide.
7. Airbnb: https://github.com/airbnb/javascript
8. JSON
9. Y

As I'm using yarn as package manager, then, I will removing package-lock.json and run: yarn on the project root to update the yarn cache.

So when we installing ESLint it came with a parser called espree that creating a data structure following the rules of standard JavaScript. Thus, we need a parser typescript-eslint that creating a data structure for typescript, that is a javascript superset. The packages for this parser was installed following the dependencies steps (@typescript-eslint/parser @typescript-eslint/eslint-plugin).

Configuring the project

editor config

At the root of the project, create the .editorconfig file with the content:

root = true

[*]
end_of_line = lf
indent_style = space
indent_size = 2
charset = utf-8
trim_trailing_whitespace = true
insert_final_newline = true

eslint config

At the root of the project, change the content of .eslintrc.json file to:

{
  "env": {
    "browser": true,
    "es6": true
  },
  "globals": {
    "Atomics": "readonly",
    "SharedArrayBuffer": "readonly"
  },
  "parser": "@typescript-eslint/parser",
  "parserOptions": {
    "ecmaFeatures": {
      "jsx": true
    },
    "ecmaVersion": 2018,
    "sourceType": "module"
  },
  "plugins": ["react", "@typescript-eslint", "prettier"],
  "extends": [
    "plugin:react/recommended",
    "airbnb",
    "plugin:prettier/recommended",
    "plugin:@typescript-eslint/eslint-recommended",
    "plugin:@typescript-eslint/recommended"
  ],
  "rules": {
    "import/extensions": [
      "error",
      "ignorePackages",
      {
        "js": "never",
        "jsx": "never",
        "ts": "never",
        "tsx": "never"
      }
    ],
    "prettier/prettier": "error",
    "@typescript-eslint/explicit-function-return-type": "off",
    "@typescript-eslint/no-unused-vars": "off",
    "react/jsx-filename-extension": [
      1,
      { "extensions": [".js", ".jsx", ".ts", ".tsx"] }
    ]
  },
  "settings": {
    "import/resolver": {
      "node": {
        "extensions": [".js", ".jsx", ".ts", ".tsx"]
      }
    }
  }
}

prettier config

At the root of the project, create the .prettierrc file with the content:

{
  "singleQuote": true,
  "trailingComma": "es5"
}

Loading svg logo in App.tsx

The import svg logo in App.tsx will initialing fail. To fix that create custom.d.ts whit the content:

declare module '*.svg' {
  import React = require('react');
  export const ReactComponent: React.SFC<React.SVGProps<SVGSVGElement>>;
  const src: string;
  export default src;
}

and now reference this file in tsconfig.json like this:

"include": ["src", "custom.d.ts"]

Editing the vscode config (settings.json)

"eslint.validate": [
    "javascript",
    "javascriptreact",
    "typescript",
    "typescriptreact"
],
"[javascriptreact]": {
    "editor.codeActionsOnSave": {
      "source.fixAll.eslint": true,
    }
},
"editor.formatOnSave": true,
  "[typescript]": {
    "editor.formatOnSave": false,
    "editor.codeActionsOnSave": {
      "source.fixAll.eslint": true,
    }
},
  "[typescriptreact]": {
    "editor.formatOnSave": false,
    "editor.codeActionsOnSave": {
      "source.fixAll.eslint": true,
    }
}

Finally, rename any file to be a TypeScript file (index.js to index.tsx and App.js to App.tsx) and restart your server.

Source code