Home

Awesome

Handshake JavaScript Style Guide() {

A mostly reasonable approach to JavaScript

Other Style Guides

Table of Contents

  1. Types
  2. References
  3. Objects
  4. Arrays
  5. Destructuring
  6. Strings
  7. Functions
  8. Arrow Functions
  9. Constructors
  10. Modules
  11. Properties
  12. Variables
  13. Hoisting
  14. Comparison Operators & Equality
  15. Blocks
  16. Comments
  17. Whitespace
  18. Commas
  19. Semicolons
  20. Type Casting & Coercion
  21. Naming Conventions
  22. Accessors
  23. Events
  24. jQuery
  25. ECMAScript 5 Compatibility
  26. ECMAScript 6 Styles
  27. Testing
  28. Performance
  29. Resources
  30. In the Wild
  31. Translation
  32. The JavaScript Style Guide Guide
  33. Chat With Us About JavaScript
  34. Contributors
  35. License

Types

<a name="types--primitives"></a><a name="1.1"></a>

<a name="types--complex"></a><a name="1.2"></a>

⬆ back to top

References

<a name="references--prefer-const"></a><a name="2.1"></a>

<a name="references--disallow-var"></a><a name="2.2"></a>

<a name="references--block-scope"></a><a name="2.3"></a>

⬆ back to top

Objects

<a name="objects--no-new"></a><a name="3.1"></a>

<a name="objects--reserved-words"></a><a name="3.2"></a>

<a name="objects--reserved-words-2"></a><a name="3.3"></a>

<a name="es6-computed-properties"></a><a name="3.4"></a>

<a name="es6-object-shorthand"></a><a name="3.5"></a>

<a name="es6-object-concise"></a><a name="3.6"></a>

<a name="objects--grouped-shorthand"></a><a name="3.7"></a>

<a name="objects-quoted-props"></a><a name="3.8"></a>

Why? In general we consider it subjectively easier to read. It improves syntax highlighting, and is also more easily optimized by many JS engines.

```javascript
// bad
const bad = {
    "foo": 3,
    "bar": 4,
    "data-blah": 5,
};

// good
const good = {
    foo: 3,
    bar: 4,
    "data-blah": 5,
};
```

⬆ back to top

Arrays

<a name="arrays--literals"></a><a name="4.1"></a>

<a name="arrays--push"></a><a name="4.2"></a>

<a name="es6-array-spreads"></a><a name="4.3"></a>

<a name="arrays--from"></a><a name="4.4"></a>

<a name="arrays--callback-return"></a><a name="4.5"></a>

⬆ back to top

Destructuring

<a name="destructuring--object"></a><a name="5.1"></a>

<a name="destructuring--array"></a><a name="5.2"></a>

<a name="destructuring--object-over-array"></a><a name="5.3"></a>

⬆ back to top

Strings

<a name="strings--quotes"></a><a name="6.1"></a>

<a name="strings--line-length"></a><a name="6.2"></a>

<a name="strings--concat-perf"></a><a name="6.3"></a>

<a name="es6-template-literals"></a><a name="6.4"></a>

<a name="strings--eval"></a><a name="6.5"></a>

<a name="strings--escaping"></a>

⬆ back to top

Functions

<a name="functions--declarations"></a><a name="7.1"></a>

<a name="functions--iife"></a><a name="7.2"></a>

<a name="functions--in-blocks"></a><a name="7.3"></a>

<a name="functions--note-on-blocks"></a><a name="7.4"></a>

<a name="functions--arguments-shadow"></a><a name="7.5"></a>

<a name="es6-rest"></a><a name="7.6"></a>

<a name="es6-default-parameters"></a><a name="7.7"></a>

<a name="functions--default-side-effects"></a><a name="7.8"></a>

<a name="functions--defaults-last"></a><a name="7.9"></a>

<a name="functions--constructor"></a><a name="7.10"></a>

<a name="functions--signature-spacing"></a><a name="7.11"></a>

<a name="functions--mutate-params"></a><a name="7.12"></a>

<a name="functions--reassign-params"></a><a name="7.13"></a>

⬆ back to top

Arrow Functions

<a name="arrows--use-them"></a><a name="8.1"></a>

<a name="arrows--implicit-return"></a><a name="8.2"></a>

<a name="arrows--paren-wrap"></a><a name="8.3"></a>

<a name="arrows--one-arg-parens"></a><a name="8.4"></a>

<a name="arrows--confusing"></a><a name="8.5"></a>

⬆ back to top

Constructors

<a name="constructors--use-class"></a><a name="9.1"></a>

<a name="constructors--extends"></a><a name="9.2"></a>

<a name="constructors--chaining"></a><a name="9.3"></a>

<a name="constructors--tostring"></a><a name="9.4"></a>

<a name="constructors--no-useless"></a><a name="9.5"></a>

⬆ back to top

Modules

<a name="modules--use-them"></a><a name="10.1"></a>

<a name="modules--no-export-from-import"></a><a name="10.3"></a>

<a name="modules--no-duplicate-imports"></a>

⬆ back to top

Properties

<a name="properties--dot"></a><a name="12.1"></a>

<a name="properties--bracket"></a><a name="12.2"></a>

⬆ back to top

Variables

<a name="variables--const"></a><a name="13.1"></a>

<a name="variables--one-const"></a><a name="13.2"></a>

<a name="variables--const-let-group"></a><a name="13.3"></a>

<a name="variables--define-where-used"></a><a name="13.4"></a>

⬆ back to top

Hoisting

<a name="hoisting--about"></a><a name="14.1"></a>

<a name="hoisting--anon-expressions"></a><a name="14.2"></a>

<a name="hoisting--named-expresions"></a><a name="14.3"></a>

<a name="hoisting--declarations"></a><a name="14.4"></a>

⬆ back to top

Comparison Operators & Equality

<a name="comparison--eqeqeq"></a><a name="15.1"></a>

<a name="comparison--if"></a><a name="15.2"></a>

<a name="comparison--shortcuts"></a><a name="15.3"></a>

<a name="comparison--moreinfo"></a><a name="15.4"></a>

<a name="comparison--switch-blocks"></a><a name="15.5"></a>

Why? Lexical declarations are visible in the entire switch block but only get initialized when assigned, which only happens when its case is reached. This causes problems when multiple case clauses attempt to define the same thing.

eslint rules: no-case-declarations.

```javascript
// bad
switch (foo) {
    case 1:
        let x = 1;
        break;
    case 2:
        const y = 2;
        break;
    case 3:
        function f () {}
        break;
    default:
        class C {}
}

// good
switch (foo) {
    case 1: {
        let x = 1;
        break;
    }
    case 2: {
        const y = 2;
        break;
    }
    case 3: {
        function f () {}
        break;
    }
    case 4:
        bar();
        break;
    default: {
        class C {}
    }
}
```

<a name="comparison--nested-ternaries"></a><a name="15.6"></a>

<a name="comparison--unneeded-ternary"></a><a name="15.7"></a>

⬆ back to top

Blocks

<a name="blocks--braces"></a><a name="16.1"></a>

<a name="blocks--cuddled-elses"></a><a name="16.2"></a>

⬆ back to top

Comments

<a name="comments--multiline"></a><a name="17.1"></a>

<a name="comments--singleline"></a><a name="17.2"></a>

<a name="comments--actionitems"></a><a name="17.3"></a>

<a name="comments--fixme"></a><a name="17.4"></a>

<a name="comments--todo"></a><a name="17.5"></a>

⬆ back to top

Whitespace

<a name="whitespace--spaces"></a><a name="18.1"></a>

<a name="whitespace--before-blocks"></a><a name="18.2"></a>

<a name="whitespace--around-keywords"></a><a name="18.3"></a>

<a name="whitespace--infix-ops"></a><a name="18.4"></a>

<a name="whitespace--newline-at-end"></a><a name="18.5"></a>

<a name="whitespace--chains"></a><a name="18.6"></a>

<a name="whitespace--after-blocks"></a><a name="18.7"></a>

<a name="whitespace--padded-blocks"></a><a name="18.8"></a>

<a name="whitespace--in-parens"></a><a name="18.9"></a>

<a name="whitespace--in-brackets"></a><a name="18.10"></a>

<a name="whitespace--in-braces"></a><a name="18.11"></a>

<a name="whitespace--max-len"></a><a name="18.12"></a>

⬆ back to top

Commas

<a name="commas--leading-trailing"></a><a name="19.1"></a>

<a name="commas--dangling"></a><a name="19.2"></a>

⬆ back to top

Semicolons

<a name="semicolons--required"></a><a name="20.1"></a>

⬆ back to top

Type Casting & Coercion

<a name="coercion--explicit"></a><a name="21.1"></a>

<a name="coercion--strings"></a><a name="21.2"></a>

<a name="coercion--numbers"></a><a name="21.3"></a>

<a name="coercion--comment-deviations"></a><a name="21.4"></a>

<a name="coercion--bitwise"></a><a name="21.5"></a>

<a name="coercion--booleans"></a><a name="21.6"></a>

⬆ back to top

Naming Conventions

<a name="naming--descriptive"></a><a name="22.1"></a>

<a name="naming--camelCase"></a><a name="22.2"></a>

<a name="naming--PascalCase"></a><a name="22.3"></a>

<a name="naming--leading-underscore"></a><a name="22.4"></a>

<a name="naming--self-this"></a><a name="22.5"></a>

<a name="naming--filename-matches-export"></a><a name="22.6"></a>

<a name="naming--filename-no-redundant-prefix-postfix"></a><a name="22.6.1"></a>

<a name="naming--camelCase-default-export"></a><a name="22.7"></a>

<a name="naming--PascalCase-singleton"></a><a name="22.8"></a>

⬆ back to top

Accessors

<a name="accessors--not-required"></a><a name="23.1"></a>

<a name="accessors--boolean-prefix"></a><a name="23.3"></a>

<a name="accessors--consistent"></a><a name="23.4"></a>

⬆ back to top

Events

<a name="events--hash"></a><a name="24.1"></a>

⬆ back to top

jQuery

<a name="jquery--dollar-prefix"></a><a name="25.1"></a>

<a name="jquery--cache"></a><a name="25.2"></a>

<a name="jquery--queries"></a><a name="25.3"></a>

<a name="jquery--find"></a><a name="25.4"></a>

⬆ back to top

ECMAScript 5 Compatibility

<a name="es5-compat--kangax"></a><a name="26.1"></a>

⬆ back to top

ECMAScript 6 Styles

<a name="es6-styles"></a><a name="27.1"></a>

  1. Arrow Functions
  2. Classes
  3. Object Shorthand
  4. Object Concise
  5. Object Computed Properties
  6. Template Strings
  7. Destructuring
  8. Default Parameters
  9. Rest
  10. Array Spreads
  11. Let and Const
  12. Iterators and Generators
  13. Modules

⬆ back to top

Testing

<a name="testing--yup"></a><a name="28.1"></a>

<a name="testing--for-real"></a><a name="28.2"></a>

⬆ back to top

Performance

⬆ back to top

Resources

Learning ES6

Read This

Other Style Guides

Other Styles

Further Reading

Books

Blogs

Podcasts

⬆ back to top

License

(The MIT License)

Copyright (c) 2016 Handshake

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.

⬆ back to top

};