eslint-rules

Additional rules for eslint

no-commented-out-code

Detects code in the single or multiline comments

/* eslint no-commented-out-code:1 */
/*
function foo() {
  return 'foo';
}*/
// this is normal comment
function baz() {
  'use strict';
  // and this is another normal comment
  // var bar = 'bar';
  return 'baz';
}

Produces the following output:

 2:0  warning  commented out code "function foo() {" (4 lines)  no-commented-out-code
10:2  warning  commented out code "var bar = 'bar';" (1 line)   no-commented-out-code

no-long-files

Detect source files with too many lines

first argument: rule severity (0 - no check, 1 - warning, 2 - error)
second argument: max number of allowed lines
"no-long-files": [2, 70]

Prints something like

potential-point-free.js
  0:0  error  file line count 51 exceeded line limit 50  no-long-files

camel_case

ESLint rule for enforcing camelCame names but allowing _ in property names

We want to use camelCase in variable names, but want to still allow underscores in JSON objects:

var goodObject = {
  property_name: 1,
  another_property: 2
};

jshint has camelcase rule that forces EVERY name to be camelCased

$ jshint index.js
index.js: line 2, col 0, Identifier 'property_name' is not in camel case.
index.js: line 3, col 0, Identifier 'another_property' is not in camel case.
2 errors

There are manual workarounds:

• disable this specific rule using // jshint ignore:lint or // jshint -W106
• write property names using quotes, for example 'property_name': 1

Both workarounds are hacky.

I wrote a more flexible rule called camel_case for eslint. The rule looks one character after the identifier to see if it is followed by colon : character. If yes, this is a property name inside an object, and underscore character _ is allowed.

no-for-loops

Warns or errors if you use for loops in your code. I consider for loops harmful for their side effects, and even consider .forEach dangerous, see Avoid forEach.

no-single-line-objects

Does not allow you to nest objects into single line. Single property object can be single line

// allowed
var foo = { foo: 'foo' };
// not allowed
var foo = { foo: 'foo', bar: 'bar' };
var foo = { foo: { bar: 'bar' } };

potential-point-free

Warns if a function just calls another function passing arguments and can potentially become point-free. Point-free programming eliminates complexity and superfluous variables. Only functions with single call expression are considered. The arguments must match exactly.

/* eslint potential-point-free:1 */
function print(x) {
  console.log(x);
}
[1, 2, 3].forEach(function printX(x) {
  print(x);
});
// output 7:18  warning  printX   potential-point-free

Note: due to signatures and optional arguments, sometimes functions should not be point free directly. For example the array iterators pass item, index and the array itself, which causes problems for parseInt

['1', '2', '3'].forEach(parseInt);
// [1, 'NaN', 'NaN']

In this case, you can use unary adaptor or 3rd party iterator with simpler signature, R.forEach.

running

Place camel_case.js into local folder, pass to eslint using --rulesdir option. Enable camel_case rule from .eslintrc file

// .eslintrc
{
  // 0 - turn rule off
  // 1 - rule generates warnings
  // 2 - rule generates errors
  "rules": {
    "camel_case": 2,
    // other rules
  }
}
// run
eslint index.js --rulesdir .

Small print

Author: Gleb Bahmutov © 2014

• @bahmutov
• glebbahmutov.com
• blog

License: MIT - do anything with the code, but don't blame me if it does not work.

Spread the word: tweet, star on github, etc.

Support: if you find any problems with this module, email / tweet / open issue on Github

MIT License

Copyright (c) 2014 Gleb Bahmutov

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.