guseyn / art-of-naming-variables

My version of this spec.

The art of naming variables (My variation)

Arrays

// bad
const fruit = ['apple', 'banana', 'cucumber']

// bad
const fruitArr = ['apple', 'banana', 'cucumber']

// bad
const fruits = ['apple', 'banana', 'cucumber']

// great - "names" implies strings
const fruitNames = ['apple', 'banana', 'cucumber']

// great
const fruits = [{
    name: 'apple',
    genus: 'malus'
}, {
    name: 'banana',
    genus: 'musa'
}, {
    name: 'cucumber',
    genus: 'cucumis'
}]

Booleans

Booleans can hold only 2 values, true or false. Given this, using prefixes like “is”, “has”, and “can” will help the reader infer the type of the variable. But it also specify context of the variable like a noun that the boolean variable is attached to.

// bad
const open = true
const write = true
const fruit = true

// bad
const isOpen = true
const canWrite = true
const hasFruit = true
const wasEgg = true
const eatAble = true
const haveCustomFilters = true
const hasCustomFilter = true
const areCustomFiltersApplied = true
const isCustomFilterApplied = true

// good
const itIsOpen = true
const itCanWrite = true
const itHasFruit = true
const itWasEgg = true
const itIsEatAble = true
const itHasCustomFilters = true
const itHasCustomFilter = true
const thereAreCustomFiltersApplied = true
const itIsCustomFilterApplied = true

it can be replaced for the context with concrete noun.

And then you can use with if statement, and it would look natural in English:

if (doorIsOpen) {
  // close it
}

Functions

What about predicate functions (functions that return booleans)?

const checkWhetherItHasFruit = (user, fruitName) => (
    user.fruits.includes(fruitName)
);
const itHasFruit = checkWhetherItHasFruit(user, 'apple')

Functions should be named using a verb if they return void, and a noun if they return something. When functions perform some type of action on a resource, its name should reflect that. A good format to follow is actionResource. For example, getUser.

// bad
getUser(db)
getUser(xml)

// good
const userRetrievedFromDB = userFromDB()
const userParsedFromXML = userFromXML()