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Last active Jan 13, 2020

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Tiny rules for how to name things in CSS and JS

Tiny rules for how to name stuff


How to name CSS classes

Stateful Class names

Is it a state that is only one of two conditions? (i.e. a boolean)

  • Prefix with is/has

Is it a state that is determined by something on its own element?

  • use .is; that describes the element's own state

e.g. .isOverflowHidden .isHidden .isScrollable

Is it a state that is determined by its children?

  • use .has; this describes the state of something inside the element
  • try to make the end part a noun

e.g. .hasOverflowHidden .hasHiddenChildren .hasScrollableChildren

Is it a state that is a negative ?

  • if you can, avoid this because it can be hard to use; try to re-write as a positive
  • Use isNot and/or hasNo
  • Use an adjective for "is"
  • Try to stick a noun at the end for "has"; "Els" is a fine abbreviation for elements
  • if all else fails, add "able"

e.g.: .isNotHidden, .hasNoHiddenEls .isNotScrollable, .hasNoScrollable, .hasNoScrollableEls

Is it a CSS class that JavaScript needs?

  • Prefix with js/ui

Does JavaScript need it just to find it (no CSS being set)?

  • use .js

e.g. .jsSubmitButton .jsVideoPlay

Does JavaScript need to change it so that CSS can style it?

  • use .ui
  • use an adjective or a past-tense

e.g. .uiSubmitted .uiVideoPlayed

Does a Test need it?

  • use .qa

Should I Use hyphens or underscores to separate a class prefix?

  • Be consistent
  • If everyone else is using hyphens, you should, too.
  • If you're the first person on the project, use camelCase; it's easier to select camelCased text in an IDE than it is hyphenated text

Is this a SRP (single responsibility principle) kind of class?

Sometimes a class only has one property because it's used in combination with other classes.

  • Don't use the value of a specific CSS property
  • Do give the purpose of that specific CSS property
  • Avoid suggesting usage with only specific HTML elements
  • Try suggesting usage with kinds of content

e.g. Avoid this:

 .button--yellow {
  color: yellow;

And instead try this:

 .button--warn {
   color: yellow 

Avoid this:

 .imgFloatLeft {
  float: left;
 .imgFloatRight {
  float: right;

And instead try

.rtfMedia--left {
 float: left;

.rtfMedia--right {
 float: right;

Sass/SCSS/Stylus/CSS naming

Variables for Colors

  • don't let the variable name indicate the variable value (what if the value changes)

  • indicate relative aspects of the value like hue, lightness

  • use relatives and superlatives (er, est) for variations on a hue


Generic Variables

Is the variable going to be used more than once?

  • start with the UI element name

  • end with the CSS property it affects

  • never put any information about the value of the variable in the name

      $linkColor: rgb(165,220,220,220)
      --linkColor: var(--colorCoolDark)

Is this variable used more than once, but there's a different variable for pseudo classes?

  • start with the UI element name

  • Then add the CSS property it affects

  • End with the state

      $linkColor: rgb(165,220,220);
      $linkColorHover: rgb(165,165,220);
      --linkColorHover: var(--colorCoolDarker);

Is the variable used once?

  • start with class name that the variable is used in

  • end with the CSS property it affects

      .foo {
          $fooHeight: $containerHeight / 3;
          width: $fooHeight / 2;
          height: $fooHeight;

JS Naming

Functions that return things

Does the function return a boolean?

  • Prefix with "is" or "has"
  • Use "is" with an adjective
  • Use "has" with a noun
  • Avoid using a negative


function isHot() {
 if (temperature > 100 ) {
   return false;
 } else {
   return true;

function hasEggs(carton) { 
  if (carton.eggs.length > 0 ) { 
    return true;
  } else { 
    return false;

Does the function return anything else ?

  • Prefix with get

  • End with thing it returns

  • Use a plural form if it returns an enumerable

      function getTemperature () {
        return temperature;
      function getEggs() {
        const eggs = [];
        return eggs;

Are you assigning the thing that the function returns to a variable?

Use the noun part of the function

const foods = getFoods();
const number = addNumbers();

Functions that do things

  • Start with a verb, end with a noun
  • Make the noun the thing that is the recipient of the action:



Looping through stuff

  • Avoid using single-letter variable names (e.g. i);
  • Use at least-three letters.

Is the loop a.forEach on an array or array-like structure?

  1. Make the array's noun its plural form

  2. Make the item iterated on the singular form

     const fruits = ['banana', 'avocado', 'tomato'];
     fruits.forEach((fruit) => {

Does the .forEach need an index?

  1. Start with idx

  2. Avoid single-letter variable names

     const fruits = ['banana', 'avocado', 'tomato'];
     fruits.forEach((fruit, idx) => {

If you have to go more than one level deep, append idx to the item name:

    const foodGroups = [ ['banana', 'avocado', 'tomato'], ['steak', 'sausage' ] ];
    foodGroups.forEach((foodGroup, idx ) => {
        foodGroup.forEach((food, foodIdx) => {

Is the loop using for in or for of ?

  1. Make the object/array's noun a plural form

  2. Start any counter variables with idx

  3. If you have to go more than one level deep, append idx to the item name

     for (let idx = 0, fruit; idx < fruits.length; ++idx) {
       fruit = fruits[idx];
       for (let gfIdx = 0; goodFruit; gfIdx < goodFruits.length; ++gfIdx) {
           goodFruit = goodFruits[gfIdx]


Function / argument parity

Keep function parameters similar -- but not the same, as the function arguments:

/* parameters are firstNum, secondNum */
function addNumbers(firstNum, secondNum) {
    return firstNum + secondNum;

const first = 1;
const second = 2;
const sum = addNumbers(first, second); /* arguments are first, second */

Parameter names

  1. Don't include the type as part of the name; that's what comments are for

  2. If you feel like it's super important to include the type, put it at the beginning

    function addNumbers(numberFirst, numberSecond) {}
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