23.1 Avoid single letter names. Be descriptive with your naming. eslint: id-length
// bad
function q() {
// ...
}
// good
function query() {
// ...
}
23.2 Use camelCase when naming objects, functions, and instances. eslint: camelcase jscs: requireCamelCaseOrUpperCaseIdentifiers
// bad
const OBJEcttsssss = {};
const this_is_my_object = {};
function c() {}
// good
const thisIsMyObject = {};
function thisIsMyFunction() {}
23.3 Use PascalCase only when naming constructors or classes. eslint: new-cap jscs: requireCapitalizedConstructors
// bad
function user(options) {
this.name = options.name;
}
const bad = new user({
name: 'nope',
});
// good
class User {
constructor(options) {
this.name = options.name;
}
}
const good = new User({
name: 'yup',
});
23.4 Do not use trailing or leading underscores. eslint: no-underscore-dangle jscs: disallowDanglingUnderscores
Why? JavaScript does not have the concept of privacy in terms of properties or methods. Although a leading underscore is a common convention to mean “private”, in fact, these properties are fully public, and as such, are part of your public API contract. This convention might lead developers to wrongly think that a change won’t count as breaking, or that tests aren’t needed. tl;dr: if you want something to be “private”, it must not be observably present.
// bad
this.__firstName__ = 'Panda';
this.firstName_ = 'Panda';
this._firstName = 'Panda';
// good
this.firstName = 'Panda';
23.5 Don’t save references to this. Use arrow functions or Function#bind. jscs: disallowNodeTypes
// bad
function foo() {
const self = this;
return function () {
console.log(self);
};
}
// bad
function foo() {
const that = this;
return function () {
console.log(that);
};
}
// good
function foo() {
return () => {
console.log(this);
};
}
23.6 A base filename should exactly match the name of its default export.
// file 1 contents
class CheckBox {
// ...
}
export default CheckBox;
// file 2 contents
export default function fortyTwo() { return 42; }
// file 3 contents
export default function insideDirectory() {}
// in some other file
// bad
import CheckBox from './checkBox'; // PascalCase import/export, camelCase filename
import FortyTwo from './FortyTwo'; // PascalCase import/filename, camelCase export
import InsideDirectory from './InsideDirectory'; // PascalCase import/filename, camelCase export
// bad
import CheckBox from './check_box'; // PascalCase import/export, snake_case filename
import forty_two from './forty_two'; // snake_case import/filename, camelCase export
import inside_directory from './inside_directory'; // snake_case import, camelCase export
import index from './inside_directory/index'; // requiring the index file explicitly
import insideDirectory from './insideDirectory/index'; // requiring the index file explicitly
// good
import CheckBox from './CheckBox'; // PascalCase export/import/filename
import fortyTwo from './fortyTwo'; // camelCase export/import/filename
import insideDirectory from './insideDirectory'; // camelCase export/import/directory name/implicit "index"
// ^ supports both insideDirectory.js and insideDirectory/index.js
23.7 Use camelCase when you export-default a function. Your filename should be identical to your function’s name.
function makeStyleGuide() {
// ...
}
export default makeStyleGuide;
23.8 Use PascalCase when you export a constructor / class / singleton / function library / bare object.
const AirbnbStyleGuide = {
es6: {
},
};
export default AirbnbStyleGuide;
23.9 Acronyms and initialisms should always be all capitalized, or all lowercased.
Why? Names are for readability, not to appease a computer algorithm.
// bad
import SmsContainer from './containers/SmsContainer';
// bad
const HttpRequests = [
// ...
];
// good
import SMSContainer from './containers/SMSContainer';
// good
const HTTPRequests = [
// ...
];
// best
import TextMessageContainer from './containers/TextMessageContainer';
// best
const Requests = [
// ...
];