为什么 create-react-app 在尝试 eslint 时会给出 typescript 错误（尽管没有 typescript 文件）？

Question

I am getting this error when i do eslint.

Error: Failed to load parser '@typescript-eslint/parser' declared in '.eslintrc.yml » 
eslint-config-react-app#overrides[0]': Cannot find module 'typescript'

Answer 1

Because there are TypeScript files - although ESLint excludes node_modules/ from linting by default, CRA's override (in order to load appropriate plugins for any TypeScript files, this is why you see eslint-config-react-app#overrides[0] in the output) does include the content of node_modules/ (see eg this issue ).

You can install TypeScript, but if you don't intend to use any TypeScript files in your own source you can be more specific about what you want to lint instead. Either:

1. Change the script in package.json to only lint the source directory:

    "lint": "eslint src/"

2. Create a .eslintignore (or another file, if you set the right --ignore-path ) file containing:

    node_modules/

3. Add to the ESLint configuration object in package.json (or pass it as an --ignore-pattern ):

    "eslintConfig": { "extends": "react-app", "ignorePatterns": [ "node_modules/" ] }

The latter two options are from the documentation on configuration .

Answer 2

Install typescript

npm install --save-dev typescript

Then eslint.

will work as intended and can use the .eslintrc.yml file.

btw I had also just installed

npm install -save-save eslint-plugin-typescript

in case you are doing this as you may need that too.

btw do NOT install eslint with npm install eslint... as it may mess up due to the fact that... crewate-react-app already has it (but a lower version). so just add your eslintrc.yml file and it will work (be applied in the editor, and with this fix, at the command line as neeeded).

example output:

.../src/components/SignUp/index.js
   1:41  error  Missing semicolon                              semi
   7:26  error  Unnecessary parentheses around expression      no-extra-parens
  15:2   error  Missing semicolon                              semi
  32:13  error  'username' is assigned a value but never used  no-unused-vars
  47:63  error  Missing semicolon                              semi
  95:26  error  Unnecessary parentheses around expression      no-extra-parens