- 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.
You can install ESLint using npm:
npm install -g eslint
If it's your first time using ESLint, you should set up a config file using
eslint test.js test2.js
eslint --init, you'll have a
.eslintrc file in your directory. In it, you'll see some rules configured like this:
"quotes" are the names of rules in ESLint. The number is the error level of the rule and can be one of the three values:
0- turn the rule off
1- turn the rule on as a warning (doesn't affect exit code)
2- turn the rule on as an error (exit code will be 1)
The three error levels allow you fine-grained control over how ESLint applies rules (for more configuration options and details, see the configuration docs).
These folks keep the project moving and are resources for help:
- Nicholas C. Zakas (@nzakas) - project lead
- Ilya Volodin (@ilyavolodin) - reviewer
- Brandon Mills (@btmills) - reviewer
- Gyandeep Singh (@gyandeeps) - reviewer
- Mathias Schreck (@lo1tuma) - committer
- Jamund Ferguson (@xjamundx) - committer
- Ian VanSchooten (@ianvs) - committer
- Toru Nagashima (@mysticatea) - committer
- Burak Yiğit Kaya (@byk) - committer
- Alberto Rodríguez (@alberto) - committer
We have scheduled releases every two weeks on Friday or Saturday.
Frequently Asked Questions
Why don't you like JSHint???
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.
How does ESLint performance compare to JSHint and JSCS?
ESLint is slower than JSHint, usually 2-3x slower on a single file. This is because ESLint uses Espree to construct an AST before it can evaluate your code whereas JSHint evaluates your code as it's being parsed. The speed is also based on the number of rules you enable; the more rules you enable, the slower the process.
Despite being slower, we believe that ESLint is fast enough to replace JSHint without causing significant pain.
ESLint is faster than JSCS, as ESLint uses a single-pass traversal for analysis whereas JSCS using a querying model.
If you are using both JSHint and JSCS on your files, then using just ESLint will be faster.
Is ESLint just linting or does it also check style?
ESLint does both traditional linting (looking for problematic patterns) and style checking (enforcement of conventions). You can use it for both.
What about ECMAScript 6 support?
ESLint has full support for ECMAScript 6. By default, this support is off. You can enable ECMAScript 6 support through configuration.
Does ESLint support JSX?
Yes, ESLint natively supports parsing JSX syntax (this must be enabled in configuration.). Please note that supporting JSX syntax is not the same as supporting React. React applies specific semantics to JSX syntax that ESLint doesn't recognize. We recommend using eslint-plugin-react if you are using React and want React semantics.
What about ECMAScript 7/2016 and experimental features?
ESLint doesn't natively support experimental ECMAScript language features. You can use babel-eslint to use any option available in Babel.