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Grooveshark JavaScript Style Guide() {

A mostly reasonable approach to JavaScript

Forked and slightly modified from Airbnb's Style Guide, but still reasonable

<a name='TOC'>Table of Contents</a>

  1. Types
  2. Objects
  3. Arrays
  4. Strings
  5. Functions
  6. Properties
  7. Variables
  8. Hoisting
  9. Conditional Expressions & Equality
  10. Blocks
  11. Comments
  12. Whitespace
  13. Commas
  14. Semicolons
  15. Type Casting & Coercion
  16. Naming Conventions
  17. Accessors
  18. Constructors
  19. Events
  20. jQuery
  21. ES5 Compatibility
  22. Testing
  23. Performance
  24. Resources
  25. In the Wild
  26. Translation
  27. The JavaScript Style Guide Guide
  28. Contributors
  29. License

<a name='types'>Types</a>

<a name='objects'>Objects</a>

<a name='arrays'>Arrays</a>

<a name='strings'>Strings</a>

<a name='functions'>Functions</a>

<a name='properties'>Properties</a>

<a name='variables'>Variables</a>

<a name='hoisting'>Hoisting</a>

<a name='conditionals'>Conditional Expressions & Equality</a>

<a name='blocks'>Blocks</a>

<a name='comments'>Comments</a>


  **[[⬆]](#TOC)**


## <a name='whitespace'>Whitespace</a>

- Use soft tabs set to 4 spaces

  ```javascript
  // bad
  function() {
  ∙∙var name;
  }

  // bad
  function() {
  ∙var name;
  }

  // good
  function() {
  ∙∙∙∙var name;
  }
  ```
- Place 1 space before the leading brace.

  ```javascript
  // bad
  function test(){
      console.log('test');
  }

  // good
  function test() {
      console.log('test');
  }

  // bad
  dog.set('attr',{
      age: '1 year',
      breed: 'Bernese Mountain Dog'
  });

  // good
  dog.set('attr', {
      age: '1 year',
      breed: 'Bernese Mountain Dog'
  });
  ```
- Place an empty newline at the end of the file.

  ```javascript
  // bad
  (function(global) {
      // ...stuff...
  })(this);
  ```

  ```javascript
  // good
  (function(global) {
      // ...stuff...
  })(this);

  ```

  **[[⬆]](#TOC)**

## <a name='commas'>Commas</a>

- Leading commas: **Nope.**

  ```javascript
  // bad
  var once
    , upon
    , aTime;

  // good
  var once,
      upon,
      aTime;

  // bad
  var hero = {
      firstName: 'Bob'
    , lastName: 'Parr'
    , heroName: 'Mr. Incredible'
    , superPower: 'strength'
  };

  // good
  var hero = {
      firstName: 'Bob',
      lastName: 'Parr',
      heroName: 'Mr. Incredible',
      superPower: 'strength'
  };
  ```

- Additional trailing comma: **Nope.** This can cause problems with IE6/7 and IE9 if it's in quirksmode. Also, in some implementations of ES3 would add length to an array if it had an additional trailing comma. This was clarified in ES5 ([source](http://es5.github.io/#D)):

> Edition 5 clarifies the fact that a trailing comma at the end of an ArrayInitialiser does not add to the length of the array. This is not a semantic change from Edition 3 but some implementations may have previously misinterpreted this.

  ```javascript
  // bad
  var hero = {
      firstName: 'Kevin',
      lastName: 'Flynn',
  };

  var heroes = [
      'Batman',
      'Superman',
  ];

  // good
  var hero = {
      firstName: 'Kevin',
      lastName: 'Flynn'
  };

  var heroes = [
      'Batman',
      'Superman'
  ];
  ```

  **[[⬆]](#TOC)**


## <a name='semicolons'>Semicolons</a>

- **Yup.**

  ```javascript
  // bad
  (function() {
      var name = 'Skywalker'
      return name
  })()

  // good
  (function() {
      var name = 'Skywalker';
      return name;
  })();
  ```

  **[[⬆]](#TOC)**


## <a name='type-coercion'>Type Casting & Coercion</a>

- Perform type coercion at the beginning of the statement.
- Strings:

  ```javascript
  //  => this.reviewScore = 9;

  // bad
  var totalScore = this.reviewScore + '';

  // good
  var totalScore = '' + this.reviewScore;

  // bad
  var totalScore = '' + this.reviewScore + ' total score';

  // good
  var totalScore = this.reviewScore + ' total score';
  ```

- Use `parseInt` for Numbers and always with a radix for type casting, if you want invalid value to be NaN or the radix is not 10.
- If you want invalid values to return 0 and it is a decimal value, use Grooveshark's custom method ```_.toInt()```

  ```javascript
  var inputValue = '4';

  // bad
  var val = new Number(inputValue);

  // bad
  var val = +inputValue;

  // bad
  var val = inputValue >> 0;

  // bad
  var val = parseInt(inputValue);

  // good
  var val = Number(inputValue);

  // good
  var val = parseInt(inputValue, 10);

  // good
  var val = _.toInt(inputValue);
  ```

- If for whatever reason you are doing something wild and `parseInt` is your bottleneck and need to use Bitshift for [performance reasons](http://jsperf.com/coercion-vs-casting/3), don't.
- Use Grooveshark's custom method _.toInt() instead - it uses bitshifting for performance in the browsers for which it makes a difference.

- Booleans:

  ```javascript
  var age = 0;

  // bad
  var hasAge = new Boolean(age);

  // good
  var hasAge = Boolean(age);

  // good
  var hasAge = !!age;
  ```

  **[[⬆]](#TOC)**


## <a name='naming-conventions'>Naming Conventions</a>

- Avoid single letter names. Be descriptive with your naming.

  ```javascript
  // bad
  function q() {
      // ...stuff...
  }

  // good
  function query() {
      // ..stuff..
  }
  ```

- Use headlessCamels when naming objects, functions, and instances

  ```javascript
  // bad
  var OBJEcttsssss = {};
  var this_is_my_object = {};
  var this-is-my-object = {};
  function c() {};
  var u = new user({
      name: 'Bob Parr'
  });

  // good
  var thisIsMyObject = {};
  function thisIsMyFunction() {};
  var user = new User({
      name: 'Bob Parr'
  });
  ```

- Use ProudCamels when naming constructors or classes

  ```javascript
  // bad
  function user(options) {
      this.name = options.name;
  }

  var bad = new user({
      name: 'nope'
  });

  // good
  function User(options) {
      this.name = options.name;
  }

  var good = new User({
      name: 'yup'
  });
  ```

- Use a leading underscore `_` when naming private properties or methods

  ```javascript
  // bad
  this.__firstName__ = 'Panda';
  this.firstName_ = 'Panda';

  // good
  this._firstName = 'Panda';
  ```

- When saving a reference to `this` use `_this`.

  ```javascript
  // bad
  function() {
      var self = this;
      return function() {
          console.log(self);
      };
  }

  // bad
  function() {
      var that = this;
      return function() {
          console.log(that);
      };
  }

  // good
  function() {
      var _this = this;
      return function() {
          console.log(_this);
      };
  }
  ```

- Name your functions. This is helpful for stack traces.

  ```javascript
  // bad
  var log = function(msg) {
      console.log(msg);
  };

  // good
  var log = function log(msg) {
      console.log(msg);
  };
  ```

  **[[⬆]](#TOC)**


## <a name='accessors'>Accessors</a>

- Accessor functions for properties are not required
- If you do make accessor functions use getVal() and setVal('hello')
- Grooveshark Note: Nope - Use a Backbone Model if you need getters/setters

  ```javascript
  // bad
  dragon.age();

  // good
  dragon.getAge();

  // bad
  dragon.age(25);

  // good
  dragon.setAge(25);
  ```

- If the property is a boolean, use isVal() or hasVal()

  ```javascript
  // bad
  if (!dragon.age()) {
      return false;
  }

  // good
  if (!dragon.hasAge()) {
      return false;
  }
  ```

- It's okay to create get() and set() functions, but be consistent.

  ```javascript
  function Jedi(options) {
      options || (options = {});
      var lightsaber = options.lightsaber || 'blue';
      this.set('lightsaber', lightsaber);
  }

  Jedi.prototype.set = function(key, val) {
      this[key] = val;
  };

  Jedi.prototype.get = function(key) {
      return this[key];
  };
  ```

  **[[⬆]](#TOC)**


## <a name='constructors'>Constructors</a>

- Assign methods to the prototype object, instead of overwriting the prototype with a new object. Overwriting the prototype makes inheritance impossible: by resetting the prototype you'll overwrite the base!
- Grooveshark Note: Usually you'll never have to worry about this, because Backbone

  ```javascript
  function Jedi() {
      console.log('new jedi');
  }

  // bad
  Jedi.prototype = {
      fight: function fight() {
          console.log('fighting');
      },

      block: function block() {
          console.log('blocking');
      }
  };

  // good
  Jedi.prototype.fight = function fight() {
      console.log('fighting');
  };

  Jedi.prototype.block = function block() {
      console.log('blocking');
  };
  ```

- Methods can return `this` to help with method chaining.

  ```javascript
  // bad
  Jedi.prototype.jump = function() {
      this.jumping = true;
      return true;
  };

  Jedi.prototype.setHeight = function(height) {
      this.height = height;
  };

  var luke = new Jedi();
  luke.jump(); // => true
  luke.setHeight(20) // => undefined

  // good
  Jedi.prototype.jump = function() {
      this.jumping = true;
      return this;
  };

  Jedi.prototype.setHeight = function(height) {
      this.height = height;
      return this;
  };

  var luke = new Jedi();

  luke.jump()
    .setHeight(20);
  ```


- It's okay to write a custom toString() method, just make sure it works successfully and causes no side effects.

  ```javascript
  function Jedi(options) {
      options || (options = {});
      this.name = options.name || 'no name';
  }

  Jedi.prototype.getName = function getName() {
      return this.name;
  };

  Jedi.prototype.toString = function toString() {
      return 'Jedi - ' + this.getName();
  };
  ```

  **[[⬆]](#TOC)**


## <a name='events'>Events</a>

- When attaching data payloads to events (whether DOM events or something more proprietary like Backbone events), pass a hash instead of a raw value. This allows a subsequent contributor to add more data to the event payload without finding and updating every handler for the event. For example, instead of:

  ```js
  // bad
  $(this).trigger('listingUpdated', listing.id);

  ...

  $(this).on('listingUpdated', function(e, listingId) {
      // do something with listingId
  });
  ```

  prefer:

  ```js
  // good
  $(this).trigger('listingUpdated', { listingId : listing.id });

  ...

  $(this).on('listingUpdated', function(e, data) {
      // do something with data.listingId
  });
  ```

**[[⬆]](#TOC)**


## <a name='jquery'>jQuery</a>

- Prefix jQuery object variables with a `$`.

  ```javascript
  // bad
  var sidebar = $('.sidebar');

  // good
  var $sidebar = $('.sidebar');
  ```

- Cache jQuery lookups.

  ```javascript
  // bad
  function setSidebar() {
      $('.sidebar').hide();

      // ...stuff...

      $('.sidebar').css({
          'background-color': 'pink'
      });
  }

  // good
  function setSidebar() {
      var $sidebar = $('.sidebar');
      $sidebar.hide();

      // ...stuff...

      $sidebar.css({
          'background-color': 'pink'
      });
  }
  ```

- For DOM queries use Cascading `$('.sidebar ul')` or parent > child `$('.sidebar > ul')`. [jsPerf](http://jsperf.com/jquery-find-vs-context-sel/16)
- Use `find` with scoped jQuery object queries.

  ```javascript
  // bad
  $('.sidebar', 'ul').hide();

  // bad
  $('.sidebar').find('ul').hide();

  // good
  $('.sidebar ul').hide();

  // good
  $('.sidebar > ul').hide();

  // good (slower)
  $sidebar.find('ul');

  // good (faster)
  $($sidebar[0]).find('ul');
  ```

  **[[⬆]](#TOC)**


## <a name='es5'>ECMAScript 5 Compatibility</a>

- Refer to [Kangax](https://twitter.com/kangax/)'s ES5 [compatibility table](http://kangax.github.com/es5-compat-table/)

**[[⬆]](#TOC)**


## <a name='testing'>Testing</a>

- **Yup.**

  ```javascript
  function() {
      return true;
  }
  ```

  **[[⬆]](#TOC)**


## <a name='performance'>Performance</a>

- [On Layout & Web Performance](http://kellegous.com/j/2013/01/26/layout-performance/)
- [String vs Array Concat](http://jsperf.com/string-vs-array-concat/2)
- [Try/Catch Cost In a Loop](http://jsperf.com/try-catch-in-loop-cost)
- [Bang Function](http://jsperf.com/bang-function)
- [jQuery Find vs Context, Selector](http://jsperf.com/jquery-find-vs-context-sel/13)
- [innerHTML vs textContent for script text](http://jsperf.com/innerhtml-vs-textcontent-for-script-text)
- [Long String Concatenation](http://jsperf.com/ya-string-concat)
- Loading...

**[[⬆]](#TOC)**


## <a name='resources'>Resources</a>


**Read This**

- [Annotated ECMAScript 5.1](http://es5.github.com/)

**Other Styleguides**

- [Google JavaScript Style Guide](http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml)
- [jQuery Core Style Guidelines](http://docs.jquery.com/JQuery_Core_Style_Guidelines)
- [Principles of Writing Consistent, Idiomatic JavaScript](https://github.com/rwldrn/idiomatic.js/)

**Other Styles**

- [Naming this in nested functions](https://gist.github.com/4135065) - Christian Johansen
- [Conditional Callbacks](https://github.com/airbnb/javascript/issues/52)

**Further Reading**

- [Understanding JavaScript Closures](http://javascriptweblog.wordpress.com/2010/10/25/understanding-javascript-closures/) - Angus Croll

**Books**

- [JavaScript: The Good Parts](http://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockford/dp/0596517742) - Douglas Crockford
- [JavaScript Patterns](http://www.amazon.com/JavaScript-Patterns-Stoyan-Stefanov/dp/0596806752) - Stoyan Stefanov
- [Pro JavaScript Design Patterns](http://www.amazon.com/JavaScript-Design-Patterns-Recipes-Problem-Solution/dp/159059908X)  - Ross Harmes and Dustin Diaz
- [High Performance Web Sites: Essential Knowledge for Front-End Engineers](http://www.amazon.com/High-Performance-Web-Sites-Essential/dp/0596529309) - Steve Souders
- [Maintainable JavaScript](http://www.amazon.com/Maintainable-JavaScript-Nicholas-C-Zakas/dp/1449327680) - Nicholas C. Zakas
- [JavaScript Web Applications](http://www.amazon.com/JavaScript-Web-Applications-Alex-MacCaw/dp/144930351X) - Alex MacCaw
- [Pro JavaScript Techniques](http://www.amazon.com/Pro-JavaScript-Techniques-John-Resig/dp/1590597273) - John Resig
- [Smashing Node.js: JavaScript Everywhere](http://www.amazon.com/Smashing-Node-js-JavaScript-Everywhere-Magazine/dp/1119962595) - Guillermo Rauch

**Blogs**

- [DailyJS](http://dailyjs.com/)
- [JavaScript Weekly](http://javascriptweekly.com/)
- [JavaScript, JavaScript...](http://javascriptweblog.wordpress.com/)
- [Bocoup Weblog](http://weblog.bocoup.com/)
- [Adequately Good](http://www.adequatelygood.com/)
- [NCZOnline](http://www.nczonline.net/)
- [Perfection Kills](http://perfectionkills.com/)
- [Ben Alman](http://benalman.com/)
- [Dmitry Baranovskiy](http://dmitry.baranovskiy.com/)
- [Dustin Diaz](http://dustindiaz.com/)
- [nettuts](http://net.tutsplus.com/?s=javascript)

**[[⬆]](#TOC)**

## <a name='in-the-wild'>In the Wild</a>

This is a list of organizations that are using this style guide. Send us a pull request or open an issue and we'll add you to the list.

- **Airbnb**: [airbnb/javascript](https://github.com/airbnb/javascript)
- **American Insitutes for Research**: [AIRAST/javascript](https://github.com/AIRAST/javascript)
- **Compass Learning**: [compasslearning/javascript-style-guide](https://github.com/compasslearning/javascript-style-guide)
- **ExactTarget**: [ExactTarget/javascript](https://github.com/ExactTarget/javascript)
- **GeneralElectric**: [GeneralElectric/javascript](https://github.com/GeneralElectric/javascript)
- **GoodData**: [gooddata/gdc-js-style](https://github.com/gooddata/gdc-js-style)
- **How About We**: [howaboutwe/javascript](https://github.com/howaboutwe/javascript)
- **MinnPost**: [MinnPost/javascript](https://github.com/MinnPost/javascript)
- **ModCloth**: [modcloth/javascript](https://github.com/modcloth/javascript)
- **National Geographic**: [natgeo/javascript](https://github.com/natgeo/javascript)
- **National Park Service**: [nationalparkservice/javascript](https://github.com/nationalparkservice/javascript)
- **Razorfish**: [razorfish/javascript-style-guide](https://github.com/razorfish/javascript-style-guide)
- **Shutterfly**: [shutterfly/javascript](https://github.com/shutterfly/javascript)
- **Userify**: [userify/javascript](https://github.com/userify/javascript)
- **Zillow**: [zillow/javascript](https://github.com/zillow/javascript)
- **ZocDoc**: [ZocDoc/javascript](https://github.com/ZocDoc/javascript)

## <a name='translation'>Translation</a>

This style guide is also available in other languages:

- :de: **German**: [timofurrer/javascript-style-guide](https://github.com/timofurrer/javascript-style-guide)
- :jp: **Japanese**: [mitsuruog/javacript-style-guide](https://github.com/mitsuruog/javacript-style-guide)
- :br: **Portuguese**: [armoucar/javascript-style-guide](https://github.com/armoucar/javascript-style-guide)
- :cn: **Chinese**: [adamlu/javascript-style-guide](https://github.com/adamlu/javascript-style-guide)

## <a name='guide-guide'>The JavaScript Style Guide Guide</a>

- [Reference](https://github.com/airbnb/javascript/wiki/The-JavaScript-Style-Guide-Guide)

## <a name='authors'>Contributors</a>

- [View Contributors](https://github.com/airbnb/javascript/graphs/contributors)


## <a name='license'>License</a>

(The MIT License)

Copyright (c) 2012 Airbnb

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.

**[[⬆]](#TOC)**

# };