php1301/naming-cheatsheet

Comprehensive language-agnostic guidelines on variables naming.

Naming cheatsheet

• Naming convention
• S-I-D
• Avoid contractions
• Avoid context duplication
• Reflect expected result
• Naming functions
  • A/HC/LC pattern
    • Actions
    • Context
    • Prefixes
• Singular and Plurals

---

Naming things is hard. This sheet attempts to make it easier.

Although these suggestions can be applied to any programming language, I will use JavaScript to illustrate them in practice.

Naming convention

Pick one naming convention and follow it. It may be cammelCase, or snake_case, or anyhow else, it does not matter. What matters is for it to remain consistent.

/* Bad */
const pages_count = 5
const shouldUpdate = true

/* Good */
const pagesCount = 5
const shouldUpdate = true

/* Good as well */
const pages_count = 5
const should_update = true

S-I-D

A name must be short, intuitive and descriptive:

• Short. A name must not take long to type and, therefore, remember;
• Intuitive. A name must read naturally, as close to the common speech as possible;
• Descriptive. A name must reflect what it does/possesses in the most efficient way.

/* Bad */
const a = 5 // "a" could mean anything
const isPaginatable = postsCount > 10 // "Paginatable" sounds extremely unnatural
const shouldPaginatize = postsCount > 10 // Made up verbs are so much fun!

/* Good */
const postsCount = 5
const hasPagination = postsCount > 10
const shouldDisplayPagination = postsCount > 10 // alternatively

Avoid contractions

Do not use contractions. They contribute to nothing but decreased readability of the code. Finding a short, descriptive name may be hard, but contraction is not an excuse for not doing so.

/* Bad */
const onItmClk = () => {}

/* Good */
const onItemClick = () => {}

Avoid context duplication

A name should not duplicate the context in which it is defined. Always remove the context from a name if that doesn't decrease its readability.

class MenuItem {
  /* Method name duplicates the context (which is "MenuItem") */
  handleMenuItemClick = (event) => { ... }

  /* Reads nicely as `MenuItem.handleClick()` */
  handleClick = (event) => { ... }
}

Reflect expected result

A name should reflect the expected result.

/* Bad */
const isEnabled = itemsCount > 3
return <Button disabled={!isEnabled} />

/* Good */
const isDisabled = itemsCount <= 3
return <Button disabled={isDisabled} />

---

Naming functions

A/HC/LC Pattern

There is a useful pattern to follow when naming functions:

prefix? + action (A) + high context (HC) + low context? (LC)

Take a look at how this pattern may be applied in the table below.

Name	Prefix	Action (A)	High context (HC)	Low context (LC)
getPost		get	Post
getPostData		get	Post	Data
handleClickOutside		handle	Click	Outside
shouldDisplayMessage	should	Display	Message

Note: The order of context affects the meaning of a variable. For example, shouldUpdateComponent means you are about to update a component, while shouldComponentUpdate tells you that component will update on itself, and you are but controlling whether it should do that right now. In other words, high context emphasizes the meaning of a variable.

---

Actions

The verb part of your function name. The most important part responsible for describing what the function does.

get

Accesses data immediately (i.e. shorthand getter of internal data).

function getFruitsCount() {
  return this.fruits.length
}

See also compose.

set

Declaratively sets a variable with value A to value B.

const fruits = 0

function setFruits(nextFruits) {
  fruits = nextFruits
}

setFruits(5)
console.log(fruits) // 5

reset

Sets a variable back to its initial value or state.

const initialFruits = 5
const fruits = initialFruits
setFruits(10)
console.log(fruits) // 10

function resetFruits() {
  fruits = initialFruits
}

resetFruits()
console.log(fruits) // 5

fetch

Requests for a data, which takes time (i.e. async request).

function fetchPosts(postCount) {
  return fetch('https://api.dev/posts', {...})
}

remove

Removes something from somewhere.

For example, if you have a collection of selected filters on a search page, removing one of them from the collection is removeFilter, not deleteFilter (and this is how you would naturally say it in English as well):

function removeFilter(filterName, filters) {
  return filters.filter((name) => name !== filterName)
}

const selectedFilters = ['price', 'availability', 'size']
removeFilter('price', selectedFilters)

See also delete.

delete

Completely erazes something from the realms of existence.

Imagine you are a content editor, and there is that notorious post you wish to get rid of. Once you clicked a shiny "Delete post" button, the CMS performed a deletePost action, not removePost.

function deletePost(id) {
  return database.find({ id }).delete()
}

See also remove.

compose

Creates new data from the existing one. Mostly applicable to strings, objects, or functions.

function composePageUrl(pageName, pageId) {
  return `${pageName.toLowerCase()}-${pageId}`
}

See also get.

handle

Handles an action. Often used when naming a callback method.

function handleLinkClick() {
  console.log('Clicked a link!')
}

link.addEventListener('click', handleLinkClick)

---

Context

A domain that a function operates on.

A function is often an action on something. It is important to state what is its operable domain, or at least an expected data type.

/* A pure function operating with primitives */
function filter(predicate, list) {
  return list.filter(predicate)
}

/* Function operating exactly on posts */
function getRecentPosts(posts) {
  return filter(posts, (post) => post.date === Date.now())
}

Some language-specific assumptions may allow omitting the context. For example, in JavaScript, it's common that filter operates on Array. Adding explicit filterArray would be unnecessary.

--

Prefixes

Prefix enhances the meaning of a variable. It is rarely used in function names.

is

Describes a characteristic or state of the current context (usually boolean).

const color = 'blue'
const isBlue = color === 'blue' // characteristic
const isPresent = true // state

if (isBlue && isPresent) {
  console.log('Blue is present!')
}

has

Describes whether the current context possesses a certain value or state (usually boolean).

/* Bad */
const isProductsExist = productsCount > 0
const areProductsPresent = productsCount > 0

/* Good */
const hasProducts = productsCount > 0

should

Reflects a positive conditional statement (usually boolean) coupled with a certain action.

function shouldUpdateUrl(url, expectedUrl) {
  return url !== expectedUrl
}

min/max

Represent minimum or maximum value. Used when describing boundaries or limits.

/**
 * Renders random amount of posts within
 * the given min/max boundaries.
 */
function renderPosts(posts, minPosts, maxPosts) {
  return posts.slice(0, randomBetween(minPosts, maxPosts))
}

prev/next

Indicate the previous or the next state of a variable in the current context. Used when describing state transitions.

function fetchPosts() {
  const prevPosts = this.state.posts

  const fetchedPosts = fetch('...')
  const nextPosts = concat(prevPosts, fetchedPosts)

  this.setState({ posts: nextPosts })
}

Singular and Plurals

Like a prefix, variable names can be made singular or plural depending on whether they hold a single value or multiple values.

/* Bad */
const friends = 'Bob'
const friend = ['Bob', 'Tony', 'Tanya']

/* Good */
const friend = 'Bob'
const friends = ['Bob', 'Tony', 'Tanya']