ESLint Integration with VS Code

Learn how to integrate and configure ESLint in VS Code.

Extending an ESLint configuration

Following are the steps to extend an ESLint configuration:

  • ESLint is now perfectly suited for palindromes.js, but if you try to run it against palindromes.test.js, it won’t go well:

    $ npx eslint palindromes.test.js
    
    /Users/tburnham/code/test-driven-palindromes/palindromes.test.js
      3:1  error  'describe' is not defined  no-undef
      4:3  error  'it' is not defined        no-undef
      5:5  error  'expect' is not defined    no-undef
    
    ✖ 3 problems (3 errors, 0 warnings)
    

    All of these problems share the same cause as the module kerfuffle earlier: ESLint doesn’t know that palindromes.test.js will be running in an environment (Jest) where describe, it, and expect are defined as globals.

  • You could fix the problem with another env entry, but there’s a better way. Jest has an official ESLint plugin, eslint-plugin-jest, which comes with several rules for identifying common test code mistakes. Go ahead and add it to the project:

    $ npm install --save-dev eslint-plugin-jest@22.1.2
    + eslint-plugin-jest@22.1.2
    
  • To apply the plugin, you need to make two ...

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