GitHub - jtfmumm/javascript: JavaScript Style Guide
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## Whitespace
- 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
falcon.set("attr",{
age: "1 year",
breed: "Maltese"
});
// good
falcon.set("attr", {
age: "1 year",
breed: "Maltese"
});
```
- Set off operators with spaces.
```javascript
// bad
var x=y+5;
// good
var x = y + 5;
```
- Use indentation when making long method chains.
```javascript
// 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);
```
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## Commas
- Leading commas: **Nope.**
```javascript
// bad
var hero = {
firstName: "Immanuel"
, lastName: "Kant"
, birthPlace: "Koenigsberg"
, masterWork: "The Critique of Pure Reason"
};
// good
var hero = {
firstName: "Immanuel",
lastName: "Kant",
birthPlace: "Koenigsberg",
masterWork: "The Critique of Pure Reason"
};
```
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## Semicolons
- **Yup.**
```javascript
// bad
(function() {
var name = "Ada"
return name
})()
// good
(function() {
var name = "Ada";
return name;
})();
```
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## Type Casting & Coercion
- 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 = Number(inputValue);
// good
var val = parseInt(inputValue, 10);
```
- 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), leave a comment explaining why and what you're doing.
```javascript
// good
/**
* parseInt was the reason my code was slow.
* Bitshifting the String to coerce it to a
* Number made it a lot faster.
*/
var val = inputValue >> 0;
```
- **Note:** Be careful when using bitshift operations. Numbers are represented as [64-bit values](http://es5.github.io/#x4.3.19), but Bitshift operations always return a 32-bit integer ([source](http://es5.github.io/#x11.7)). Bitshift can lead to unexpected behavior for integer values larger than 32 bits. [Discussion](https://github.com/airbnb/javascript/issues/109). Largest signed 32-bit Int is 2,147,483,647:
```javascript
2147483647 >> 0 //=> 2147483647
2147483648 >> 0 //=> -2147483648
2147483649 >> 0 //=> -2147483647
```
- Booleans:
```javascript
var age = 0;
// bad
var hasAge = new Boolean(age);
// good
var hasAge = Boolean(age);
// good
var hasAge = !!age;
```
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## Naming Conventions
- 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 = {};
function c() {}
var u = new user({
name: "Ada Lovelace"
});
// good
var thisIsMyObject = {};
function thisIsMyFunction() {}
var user = new User({
name: "Ada Lovelace"
});
```
- 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 all caps separated by underscores for constant names
```javascript
// bad
cpuSpeed = 1e12;
//good
CPU_SPEED = 1e12;
```
- 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);
};
}
```
- **Note:** IE8 and below exhibit some quirks with named function expressions. See [http://kangax.github.io/nfe/](http://kangax.github.io/nfe/) for more info.
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## Accessors
- Accessor functions on Backbone models do not use the getVal() pattern.
```javascript
// bad
bowie.getAlbums();
// good
bowie.albums();
```
- If the property is a boolean, use isVal() or hasVal()
```javascript
// bad
if (!bowie.albums()) {
return false;
}
// good
if (!bowie.hasAlbums()) {
return false;
}
```
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## Constructors
- 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 Writer() {
console.log("new writer");
}
// bad
Writer.prototype = {
procrastinate: function() {
console.log("procrastinating");
},
dream: function() {
console.log("dreaming");
}
};
// good
Writer.prototype.procrastinate = function() {
console.log("procrastinating");
};
Writer.prototype.dream = function() {
console.log("dreaming");
};
```
- Methods can return `this` to help with method chaining.
```javascript
// bad
Writer.prototype.resolve = function() {
this.madeResolution = true;
return true;
};
Writer.prototype.imagineMovingTo = function(destination) {
this.destination = destination;
};
var roommate = new Writer();
roommate.resolve(); // => true
roommate.imagineMovingTo("Paris") // => undefined
// good
Writer.prototype.resolve = function() {
this.madeResolution = true;
return this;
};
Writer.prototype.imagineMovingTo = function(destination) {
this.destination = destination;
return this;
};
var roommate = new Writer();
roommate.resolve()
.imagineMovingTo("Paris");
```
- It's okay to write a custom toString() method, just make sure it works successfully and causes no side effects.
```javascript
function Writer(options) {
options || (options = {});
this.name = options.name || "no name";
}
Writer.prototype.toString = function toString() {
return "Writer - " + this.name;
};
```
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## Events
**[⬆ back to top](#table-of-contents)**
## Modules
- Always declare `"use strict";` at the top of the module.
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## jQuery
- 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...
$sidebar.css({
"background-color": "pink"
});
}
```
- Scope jQuery object queries to Backbone view using this.$el.find()
```javascript
// bad
$("ul", ".sidebar").hide();
// bad
$(".sidebar").find("ul").hide();
// good
this.$el.find(".sidebar ul").hide();
// good
this.$el.find(".sidebar > ul").hide();
// good
$sidebar.find("ul").hide();
```
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## ECMAScript 5 Compatibility
- Refer to [Kangax](https://twitter.com/kangax/)'s ES5 [compatibility table](http://kangax.github.com/es5-compat-table/)
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## Testing
- **Yup.**
```javascript
function() {
return true;
}
```
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## Performance
- [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...
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## Resources
**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)
- [Popular JavaScript Coding Conventions on Github](http://sideeffect.kr/popularconvention/#javascript)
**Further Reading**
- [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
- [You Might Not Need jQuery](http://youmightnotneedjquery.com/) - Zack Bloom & Adam Schwartz
- [ES6 Features](https://github.com/lukehoban/es6features) - Luke Hoban
**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
- [Secrets of the JavaScript Ninja](http://www.amazon.com/Secrets-JavaScript-Ninja-John-Resig/dp/193398869X) - John Resig and Bear Bibeault
- [Human JavaScript](http://humanjavascript.com/) - Henrik Joreteg
- [Superhero.js](http://superherojs.com/) - Kim Joar Bekkelund, Mads Mobæk, & Olav Bjorkoy
- [JSBooks](http://jsbooks.revolunet.com/)
- [Third Party JavaScript](http://manning.com/vinegar/) - Ben Vinegar and Anton Kovalyov
**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)
**[⬆ back to top](#table-of-contents)**
## In the Wild
This is a list of organizations that are using variations of the Airbnb style guide.
- **Aan Zee**: [AanZee/javascript](https://github.com/AanZee/javascript)
- **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)
- **Digitpaint** [digitpaint/javascript](https://github.com/digitpaint/javascript)
- **ExactTarget**: [ExactTarget/javascript](https://github.com/ExactTarget/javascript)
- **Gawker Media**: [gawkermedia/javascript](https://github.com/gawkermedia/javascript)
- **GeneralElectric**: [GeneralElectric/javascript](https://github.com/GeneralElectric/javascript)
- **GoodData**: [gooddata/gdc-js-style](https://github.com/gooddata/gdc-js-style)
- **Grooveshark**: [grooveshark/javascript](https://github.com/grooveshark/javascript)
- **How About We**: [howaboutwe/javascript](https://github.com/howaboutwe/javascript)
- **Mighty Spring**: [mightyspring/javascript](https://github.com/mightyspring/javascript)
- **MinnPost**: [MinnPost/javascript](https://github.com/MinnPost/javascript)
- **ModCloth**: [modcloth/javascript](https://github.com/modcloth/javascript)
- **Money Advice Service**: [moneyadviceservice/javascript](https://github.com/moneyadviceservice/javascript)
- **National Geographic**: [natgeo/javascript](https://github.com/natgeo/javascript)
- **National Park Service**: [nationalparkservice/javascript](https://github.com/nationalparkservice/javascript)
- **Orion Health**: [orionhealth/javascript](https://github.com/orionhealth/javascript)
- **Peerby**: [Peerby/javascript](https://github.com/Peerby/javascript)
- **Razorfish**: [razorfish/javascript-style-guide](https://github.com/razorfish/javascript-style-guide)
- **SeekingAlpha**: [seekingalpha/javascript-style-guide](https://github.com/seekingalpha/javascript-style-guide)
- **reddit**: [reddit/styleguide/javascript](https://github.com/reddit/styleguide/tree/master/javascript)
- **REI**: [reidev/js-style-guide](https://github.com/reidev/js-style-guide)
- **Ripple**: [ripple/javascript-style-guide](https://github.com/ripple/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)
## The JavaScript Style Guide Guide
- [Reference](https://github.com/airbnb/javascript/wiki/The-JavaScript-Style-Guide-Guide)
## Contributors
- [View Contributors](https://github.com/airbnb/javascript/graphs/contributors)
## License
(The MIT License)
Copyright (c) 2014 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.
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# };