SALT JavaScript Style Guide() {

A mostly reasonable approach to JavaScript. Based on airbnb guide

Table of Contents

Types
Objects
Arrays
Strings
Functions
Properties
Variables
Conditional Expressions & Equality
Blocks
Comments
Whitespace
Commas
Semicolons
Type Casting & Coercion
Naming Conventions
Modules
HTML/CSS Interaction
Testing
Performance
Resources
License

Types

Primitives: When you access a primitive type you work directly on its value
- string
- number
- boolean
- null
- undefined
```
var foo = 1,
    bar = foo;

bar = 9;

console.log(foo, bar); // => 1, 9
```

Complex: When you access a complex type you work on a reference to its value

object
array
function

var foo = [1, 2],
    bar = foo;

bar[0] = 9;

console.log(foo[0], bar[0]); // => 9, 9

[⬆]

Objects

Use the literal syntax for object creation.

// bad
var item = new Object();

// good
var item = {};

Don't use reserved words as keys. It won't work in IE8. More info

// bad
var superman = {
  default: { clark: 'kent' },
  private: true
};

// good
var superman = {
  defaults: { clark: 'kent' },
  hidden: true
};

Use readable synonyms in place of reserved words.

// bad
var superman = {
  class: 'alien'
};

// bad
var superman = {
  klass: 'alien'
};

// good
var superman = {
  type: 'alien'
};

[⬆]

Arrays

Use the literal syntax for array creation

// bad
var items = new Array();

// good
var items = [];

If you don't know array length use Array#push.

var someStack = [];


// bad
someStack[someStack.length] = 'abracadabra';

// good
someStack.push('abracadabra');

When you need to copy an array use Array#slice. jsPerf

var len = items.length,
    itemsCopy = [],
    i;

// bad
for (i = 0; i < len; i++) {
  itemsCopy[i] = items[i];
}

// good
itemsCopy = items.slice();

To convert an array-like object to an array, use Array#slice.

function trigger() {
  var args = Array.prototype.slice.call(arguments);
  ...
}

[⬆]

Strings

Use single quotes '' for strings

// bad
var name = "Bob Parr";

// good
var name = 'Bob Parr';

// bad
var fullName = "Bob " + this.lastName;

// good
var fullName = 'Bob ' + this.lastName;

Strings longer than 80 characters should be written across multiple lines using string concatenation.

Note: If overused, long strings with concatenation could impact performance. jsPerf & Discussion

// bad
var errorMessage = 'This is a super long error that was thrown because of Batman. When you stop to think about how Batman had anything to do with this, you would get nowhere fast.';

// bad
var errorMessage = 'This is a super long error that \
was thrown because of Batman. \
When you stop to think about \
how Batman had anything to do \
with this, you would get nowhere \
fast.';


// good
var errorMessage = 'This is a super long error that ' +
  'was thrown because of Batman.' +
  'When you stop to think about ' +
  'how Batman had anything to do ' +
  'with this, you would get nowhere ' +
  'fast.';

When programatically building up a string, use Array#join instead of string concatenation. Mostly for IE: jsPerf.

var items,
    messages,
    length,
    i;

messages = [{
    state: 'success',
    message: 'This one worked.'
},{
    state: 'success',
    message: 'This one worked as well.'
},{
    state: 'error',
    message: 'This one did not work.'
}];

length = messages.length;

// bad
function inbox(messages) {
  items = '<ul>';

  for (i = 0; i < length; i++) {
    items += '<li>' + messages[i].message + '</li>';
  }

  return items + '</ul>';
}

// good
function inbox(messages) {
  items = [];

  for (i = 0; i < length; i++) {
    items[i] = messages[i].message;
  }

  return '<ul><li>' + items.join('</li><li>') + '</li></ul>';
}

[⬆]

Functions

Function expressions:

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

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

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

Never declare a function in a non-function block (if, while, etc). Assign the function to a variable instead. Browsers will allow you to do it, but they all interpret it differently, which is bad news bears.

Note: ECMA-262 defines a block as a list of statements. A function declaration is not a statement. Read ECMA-262's note on this issue.

// bad
if (currentUser) {
  function test() {
    console.log('Nope.');
  }
}

// good
if (currentUser) {
  var test = function test() {
    console.log('Yup.');
  };
}

Never name a parameter arguments, this will take precedence over the arguments object that is given to every function scope.

// bad
function nope(name, options, arguments) {
  // ...stuff...
}

// good
function yup(name, options, args) {
  // ...stuff...
}

[⬆]

Properties

Use dot notation when accessing properties.

var luke = {
  jedi: true,
  age: 28
};

// bad
var isJedi = luke['jedi'];

// good
var isJedi = luke.jedi;

Use subscript notation [] when accessing properties with a variable.

var luke = {
  jedi: true,
  age: 28
};

function getProp(prop) {
  return luke[prop];
}

var isJedi = getProp('jedi');

[⬆]

Variables

Always use var to declare variables. Not doing so will result in global variables. We want to avoid polluting the global namespace. Captain Planet warned us of that.
```
// bad
superPower = new SuperPower();

// good
var superPower = new SuperPower();
```

Use one var declaration for multiple variables and declare each variable on a newline.

// bad
var items = getItems();
var goSportsTeam = true;
var dragonball = 'z';

// good
var items = getItems(),
    goSportsTeam = true,
    dragonball = 'z';

Declare unassigned variables last. This is helpful when later on you might need to assign a variable depending on one of the previous assigned variables.

// bad
var i, len, dragonball,
    items = getItems(),
    goSportsTeam = true;

// bad
var i, items = getItems(),
    dragonball,
    goSportsTeam = true,
    len;

// good
var items = getItems(),
    goSportsTeam = true,
    dragonball,
    length,
    i;

Assign variables at the top of their scope. This helps avoid issues with variable declaration and assignment hoisting related issues.

// bad
function() {
  test();
  console.log('doing stuff..');

  //..other stuff..

  var name = getName();

  if (name === 'test') {
    return false;
  }

  return name;
}

// good
function() {
  var name = getName();

  test();
  console.log('doing stuff..');

  //..other stuff..

  if (name === 'test') {
    return false;
  }

  return name;
}

// bad
function() {
  var name = getName();

  if (!arguments.length) {
    return false;
  }

  return true;
}

// good
function() {
  if (!arguments.length) {
    return false;
  }

  var name = getName();

  return true;
}

[⬆]

Conditional Expressions & Equality

Use === and !== over == and !=.
Conditional expressions are evaluated using coercion with the ToBoolean method and always follow these simple rules:
- Objects evaluate to true
- Undefined evaluates to false
- Null evaluates to false
- Booleans evaluate to the value of the boolean
- Numbers evalute to false if +0, -0, or NaN, otherwise true
- Strings evaluate to false if an empty string '', otherwise true
```
if ([0]) {
  // true
  // An array is an object, objects evaluate to true
}
```

Use shortcuts.

// bad
if (name !== '') {
  // ...stuff...
}

// good
if (name) {
  // ...stuff...
}

// bad
if (collection.length > 0) {
  // ...stuff...
}

// good
if (collection.length) {
  // ...stuff...
}

For more information see Truth Equality and JavaScript by Angus Croll

[⬆]

Blocks

Use multi-line braces with all blocks.

// bad
if (test)
  return false;

// bad
if (test) return false;

// good
if (test) {
  return false;
}

// bad
function() { return false; }

// good
function() {
  return false;
}

[⬆]

Comments

Use /* ... */ for multiline comments rather than // wherever possible.
Prefixing your comments with FIXME or TODO helps other developers quickly understand if you're pointing out a problem that needs to be revisited, or if you're suggesting a solution to the problem that needs to be implemented. These are different than regular comments because they are actionable. The actions are FIXME -- need to figure this out or TODO -- need to implement.

Use /* FIXME: */ to annotate problems

function Calculator() {

  /* FIXME: shouldn't use a global here */
  total = 0;

  return this;
}

Use /* TODO: */ to annotate solutions to problems

function Calculator() {

  /* TODO: total should be configurable by an options param */
  this.total = 0;

  return this;
}


  **[[⬆]](#TOC)**


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

- Use soft tabs (spaces) set to 4 spaces

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

  // bad (improper number of spaces)
  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 = 'foo'
    return name
  })()

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

  // good
  ;(function() {
    var name = 'foo';
    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.

  ```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 = parseInt(inputValue, 10);
  ```

- Booleans:

  ```javascript
  var age = 0;

  // bad
  var hasAge = new 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 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'
  });
  ```

- 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='modules'>Modules</a>

- Avoid writing inline javascript in HTML or Dust pages whenever possible. Inline javascript is impossible to unit test, is more difficult to debug, and is not our best practice. Instead...

- All scripts should be defined as requirejs modules (http://requirejs.org/docs/api.html#define)

- Here is an example module with a dependency on jQuery
  ```javascript
  // foo.js
  
  define(['jquery'], function($) {
    return {
      logFooElements: function() {
        console.log($('.foo'));
      }
    };
  });

  ```

  This module can then be used as follows
  ```javascript
  // usingFoo.js
  
  require(['foo'], function(foo) {
    foo.logFooElements();            
  });
  ```

  **[[⬆]](#TOC)**
  
## <a name='htmlcss'>HTML/CSS Interaction</a>

-  Use a 'js-' prefix for classes in DOM elements for javascript hooks. This helps us separate javascript classes from CSS classes, thereby helping us avoid breaking javascript when making CSS changes (and vice-versa)
  
  ```html

  <!-- bad -->
  <a class="toggle-widget">Click me!</a>
  
  <!-- If you're using the 'toggle-widget' class for javascript and CSS, 
  removing this for styling changes will also break javascript -->
  
  
  
  <!-- good -->
  <a class="js-toggle-widget toggle-widget">Click me!</a>
  
  <!-- Use 'js-toggle-widget' for any javascript code required for this link. 
  Now you can edit/remove the class 'toggle-widget' for style changes without fear -->
  ```

**[[⬆]](#TOC)**

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

**We use the following for testing**
- [mocha](http://visionmedia.github.io/mocha/) (Framework)
- [chai](http://chaijs.com/) (Assertion Library)
- [blanket](http://blanketjs.org/) (Code Coverage)

Test can be written in either BDD or TDD format, using any of the assertion styles provided by chai (Should, Expect, Assert)

**[[⬆]](#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)

**[[⬆]](#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**
- [SuperheroJS](http://superherojs.com/)
- [Front-End Bookmarks](https://github.com/dypsilon/frontend-dev-bookmarks)
- [Understanding JavaScript Closures](http://javascriptweblog.wordpress.com/2010/10/25/understanding-javascript-closures/) - Angus Croll
- [Basic JavaScript for the impatient programmer](http://www.2ality.com/2013/06/basic-javascript.html) - Dr. Axel Rauschmayer

**Books**

- [JavaScript: The Good Parts](http://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockford/dp/0596517742) - Douglas Crockford
- [Eloquent Javascript](http://eloquentjavascript.net/)
- [JavaScript Patterns](http://www.amazon.com/JavaScript-Patterns-Stoyan-Stefanov/dp/0596806752) - Stoyan Stefanov
- [Maintainable JavaScript](http://www.amazon.com/Maintainable-JavaScript-Nicholas-C-Zakas/dp/1449327680) - Nicholas C. Zakas
- [Secrets of the JavaScript Ninja](http://www.amazon.com/Secrets-JavaScript-Ninja-John-Resig/dp/193398869X) - John Resig and Bear Bibeault
- [JSBooks](http://jsbooks.revolunet.com/)

**Blogs**

- [Echo JS](http://echojs.com)
- [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='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)**

# };

markthomas93/javascript-1

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