ESLint Reimagined: Creating a Linter from Scratch

Welcome, this repo is part of my youtube video about Creating your own ESLint from scratch (en-us)

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Complete source code

• Access it in app

Usage

Go to app and restore dependencies as follows:

nvm use
npm i
npm link
eslint-clone --file filename.js

Example

eslint-clone --file error.js

Outputs

Error: use "const" instead of "var"
error.js:1:1
Error: use single quotes instead of double quotes
error.js:1:12
Error: use single quotes instead of double quotes
error.js:1:23
Error: use "const" instead of "var"
error.js:2:1
Error: use single quotes instead of double quotes
error.js:3:24
Error: use "let" instead of "var"
error.js:5:1
Error: use single quotes instead of double quotes
error.js:6:25
Error: use single quotes instead of double quotes
error.js:9:25
Error: use "const" instead of "let"
error.js:15:1
Error: use single quotes instead of double quotes
error.js:15:25
Error: use single quotes instead of double quotes
error.js:17:9
Linting completed with 11 error(s).

Code fixed and saved at ./error.linted.js successfully!

Cleaning Up

npm unlink eslint-clone

Tasks

• fix the bug when replacing quotes

  • if a code have single quotes enclosing double quotes such as:

    const name = '"ana"'
    

    it'd be transformed as below and will cause a syntax error.

    const name = ''ana''
    

  • How to fix: replace it to a template string instead.

    • Input:

      '"double"'.replaceAll('"', "'");
      

    • Current Output:

      ''double''.replaceAll(''', ''');
      

    • Expected Output:

      `"double"`.replaceAll(`"`, `'`);
      

• keep line breaks
• keep comments
• keep spaces
• don't put semicolons automatically
• report missing semicolon ';'