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Shutterfly JavaScript Style Guide() {

This guide is based on airbnb Guide with adaptations from the npm style guide

<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. Comma First
  14. Semicolons
  15. Asynchronous
  16. Type Casting & Coercion
  17. Naming Conventions
  18. Accessors
  19. Constructors
  20. Errors
  21. Modules
  22. jQuery
  23. ES5 Compatability
  24. Testing
  25. Performance
  26. Resources
  27. Alternatives
  28. The JavaScript Style Guide Guide
  29. Contributors
  30. 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>

 // named function expression
 var named = function named() {
   return true;
 };

 // immediately-invoked function expression (IIFE)
 (function() {
   console.log('Welcome to the Internet. Please follow me.');
 })();

 // **avoid** anonymous function expression
 var anonymous = function() {
   return true;
 };

<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>

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

// bad if (bad) mojo ()

// good if(good) luck() ```

// bad
$('#items').find('.selected').highlight().end().find('.open').updateCount();

// good
$('#items')
  .find('.selected')
    .highlight()
    .end()
  .find('.open')
    .updateCount();

// bad
var leds = stage.selectAll('.led').data(data).enter().append("svg:svg").class('led', true)
    .attr('width',  (radius + margin) * 2).append("svg:g")
    .attr("transform", "translate(" + (radius + margin) + "," + (radius + margin) + ")")
    .call(tron.led);

// good
var leds = stage.selectAll('.led')
    .data(data)
  .enter().append("svg:svg")
    .class('led', true)
    .attr('width',  (radius + margin) * 2)
  .append("svg:g")
    .attr("transform", "translate(" + (radius + margin) + "," + (radius + margin) + ")")
    .call(tron.led);
**[[⬆]](#TOC)**

<a name='comma-first'>Comma First</a>

Yes.

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

Don't use them except in four situations:

<a name='asynchronous'>Asynchronous</a>

- The callback should always be the last argument in the list. Its first argument is the Error or null.
- Send the error message back as the first argument to the callback.

```javascript
// bad
function async(data, callback) {
    var result = doStuff()
    if(isError(result))
        throw new Error('I kill state and failed to inform')
}

// good
function async(data, callback) {
    var result = doStuff()
    if(isError(result))
        callback(result)
    else
        callback(null, result)
}
```

**[[⬆]](#TOC)**

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

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

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

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

- Use camelCase 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 PascalCase 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

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

- 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')

  ```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!

  ```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='errors'>Errors</a>

- Never throw in an asynchronous method.
- always create a new Error object as it provides a call stack for debugging

**[[⬆]](#TOC)**


## <a name='modules'>Modules</a>

- The module should start with a `!`. This ensures that if a malformed module forgets to include a final semicolon there aren't errors in production when the scripts get concatenated.
- The file should be named with camelCase, live in a folder with the same name, and match the name of the single export.
- Add a method called noConflict() that sets the exported module to the previous version.
- Always declare `'use strict';` at the top of the module.

  ```javascript
  // fancyInput/fancyInput.js

  !function(global) {
    'use strict';

    var previousFancyInput = global.FancyInput;

    function FancyInput(options) {
      options || (options = {});
    }

    FancyInput.noConflict = function noConflict() {
      global.FancyInput = previousFancyInput;
    };

    global.FancyInput = FancyInput;
  }(this);
  ```

  **[[⬆]](#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 Compatability</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>

- **Yes.**

A separate describe (object literal in the case of nodeunit) is used for each functional unit tested.  This keeps
beforeEach and afterEach relevant to the unit under test and helps to group tests.


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

  **[[⬆]](#TOC)**


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

- [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)
- Loading...

**[[⬆]](#TOC)**


## <a name='alternatives'>Alternatives</a>
This section highlights considerations when choosing an alternative style

- **comma-first**
  If your team chooses to not use comma-first then use of jslint and jshint is necessary to identify syntax errors as
  well as placing "use strict"; at the top of the functional scope to avoid global variable declarations.
  Before avoiding comma-first, consider [is there something to the
  crazy comma-first style](http://ajaxian.com/archives/is-there-something-to-the-crazy-comma-first-style)

  ``` javascript
  // ok
  var o = {
      a : "ape",
      b : "bat",
      c : "cat",
      d : "dog",
      e : "elf",
      f : "fly",
      g : "gnu",
      h : "hat",
      i : "ibu"
    },
    a = [
      [ "ape", "bat" ],
      [ "cat", "dog" ],
      [ "elf", "fly" ],
      [ "gnu", "hat" ],
      [ "ibu" ]
    ];

    // preferable
    var o =
        { a : "ape"
        , b : "bat"
        , c : "cat"
        , d : "dog"
        , e : "elf"
        , f : "fly"
        , g : "gnu"
        , h : "hat"
        , i : "ibu"
        }
      , a = [ ["ape", "bat"]
            , ["cat", "dog"]
            , ["elf", "fly"]
            , ["gnu", "hat"]
            , ["ibu"]
            ]
  ```

- **semi-colons**
  If your team does not want to rely on automatic semi-colon insertion (ASI) then it is necessary to use jslint and
  jshint to identify syntax errors and terminate function declarations with semi-colons

  ```javascript
  // bad
  function() {
      console.log(arguments.length);  // 1
  }

  (function() {
      console.log('I am an argument');
  })();

  // ok
  function() {
      console.log(argument.length); // 0
  };

  (function() {
      console.log('I am not an argument');
  })();

  // preferable
  function() {
      console.log(argument.length) // 0
  }

  ;(function() {
      console.log('I am not an argument');
  })()
  ```

  In most cases it's easier to remember (and identify) when a semi-colon is missing in front of a ( or [ at the
  beginning of a line.


## <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/)

**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](//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/)
- [net.tutsplus](http://net.tutsplus.com/?s=javascript)

**[[⬆]](#TOC)**

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

- [Reference](//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)**

# };