eslint

What is eslint?

ESLint is a static code analysis tool for identifying problematic patterns found in JavaScript code. It is primarily used for finding and fixing problems in JavaScript code, enforcing coding standards, and improving code quality.

What are eslint's main functionalities?

Linting JavaScript Files

Run ESLint on all JavaScript files in the 'src' directory and its subdirectories.

eslint 'src/**/*.js'

Fixing Problems Automatically

Automatically fix problems in JavaScript files that ESLint is capable of fixing.

eslint --fix 'src/**/*.js'

Customizable Configuration

Customize ESLint rules and extend from recommended presets in the ESLint configuration file.

{ 'extends': 'eslint:recommended', 'rules': { 'eqeqeq': 'warn', 'no-unused-vars': 'error' } }

Integrating with Build Tools

Integrate ESLint with build tools like Grunt by using the corresponding plugin.

grunt.loadNpmTasks('grunt-eslint');

Using Plugins

Extend ESLint's capabilities with plugins for specific libraries or frameworks, such as React.

{ 'plugins': ['react'], 'rules': { 'react/jsx-uses-vars': 'error' } }

Other packages similar to eslint

jshint

JSHint is a community-driven tool that detects errors and potential problems in JavaScript code. It is less configurable than ESLint and does not support custom rule creation.

jscs

JSCS is a code style linter for programmatically enforcing your style guide. It has been deprecated and merged with ESLint, which now covers its functionality.

prettier

Prettier is an opinionated code formatter that supports many languages and integrates with most editors. Unlike ESLint, it does not check for code errors but focuses on maintaining a consistent code style.

tslint

TSLint was a linter for TypeScript, providing similar functionality to ESLint but specifically for TypeScript code. It has been deprecated in favor of typescript-eslint, which allows ESLint to be used with TypeScript.

standard

Standard is a JavaScript style guide, linter, and formatter with a set of predefined rules. It enforces a strict coding standard but is less configurable than ESLint.

README

ESLint

ESLint is a tool for identifying and reporting on patterns found in ECMAScript/JavaScript code. In many ways, it is similar to JSLint and JSHint with a few exceptions:

• ESLint uses Esprima for JavaScript parsing.
• ESLint uses an AST to evaluate patterns in code.
• ESLint is completely pluggable, every single rule is a plugin and you can add more at runtime.

Alpha Version

ESLint, as of v0.1.0, is in alpha, meaning that there is some stability but you shouldn't be depending on it as your only means of code verification at this time. The alpha version is intended to gather feedback from the community, catch bugs, and determine general direction for the project.

When ESLint v0.5.0 is released, it will be in beta and will have more stability in terms of interface and API.

Installation

You can install ESLint using npm:

npm i -g eslint

Usage

eslint test.js test2.js

Frequently Asked Questions

Why don't you like JSHint???

I do like JSHint. And I like Anton. Neither of those were deciding factors in creating this tool. The fact is that I've had a dire need for a JavaScript tool with pluggable linting rules. I had hoped JSHint would be able to do this, however after chatting with Anton, I found that the planned plugin infrastructure wasn't going to suit my purpose.

I'm not giving up JSHint for this!

That's not really a question, but I got it. I'm not trying to convince you that ESLint is better than JSHint. The only thing I know is that ESLint is better than JSHint for what I'm doing. In the off chance you're doing something similar, it might be better for you. Otherwise, keep using JSHint, I'm certainly not going to tell you to stop using it.

What are the plans for ESLint?

Our first goal for ESLint is to hit rule and stability parity with JSHint so that developers can start using ESLint as part of their production toolchain. The master list of JSHint features to be implemented is maintained in this Google Docs spreadsheet. To read about plans beyond parity with JSHint, check out the ESLint Roadmap.

What about ECMAScript 6 support?

At the moment, ES6 support is turned off due to the experimental nature of the support in Esprima. There is basic support for let and const, but aside from that, the rest of the features are unsupported. We will re-evaluate ES6 support after v0.5.0.

Where to ask for help?

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