CoffeeScript: Difference between revisions

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{{Short description|Programming language which compiles to JavaScript}}

{{Infobox programming language

| name = CoffeeScript

| logo = CoffeeScript-logo.pngsvg

| paradigmparadigms = [[Multi-paradigm]]: [[prototypePrototype-based programming|prototype-based]], [[functionalFunctional programming|functional]], [[imperativeImperative programming|imperative]], [[scriptingScripting language|scripting]]

| family = [[ECMAScript]]

| released = {{start date and age|2009|12|13}}

| designer = [[Jeremy Ashkenas]]

| developer = [[Jeremy Ashkenas]]same

| released = {{startStart date and age|2009|12|13}}

| latest_release_version = {{Wikidata|property|reference|edit| Q1106819 |P348}}

| latest_release_datelatest =release {{startversion date= and age|{{Wikidata|qualifierproperty|reference|edit| Q1106819 |P348|P577}}}}

| latest release date = {{start date and age|{{Wikidata|qualifier| Q1106819 |P348|P577}}}}

| typing = [[Dynamic typing|dynamic]], [[Latent typing|implicit]]

| influenced_by = [[Haskell (programming language)|Haskell]], [[JavaScript]], [[Perl]],{{citation needed|date=January 2016}} [[Python (programming language)|Python]],<ref>https://coffeescript.org/ "CoffeeScript borrows chained comparisons from Python"</ref> [[Ruby (programming language)|Ruby]], [[YAML]]<ref name="smell">{{cite news |last1=Heller |first1=Martin |date=2011-10-18 |df=mdy |url=https://www.infoworld.com/article/2078452/turn-up-your-nose-at-dart-and-smell-the-coffeescript.html |title=Turn up your nose at Dart and smell the CoffeeScript |work=[[InfoWorld]] |access-date=2020-07-15}}</ref>

| scope = [[Scope (computer science)|lexical]]

| influenced = MoonScript, [[LiveScript]], JavaScript

| programming language = CoffeeScript

| operating_system = [[Cross-platform]]

| licenseplatform = [[MIT Licensex86-64]]

| operating system = [[Cross-platform software|Cross-platform]]

| file_ext = .coffee, .litcoffee{{citation needed|date=September 2020}}

| license = [[MIT License|MIT]]

| file_extfile ext = <code>.coffee</code>, <code>.litcoffee</code>{{citation needed|date=September 2020}}

| influenced_byinfluenced by = [[Haskell (programming language)|Haskell]], [[JavaScript]], [[Perl]],{{citation needed|date=January 2016}} [[Python (programming language)|Python]],<ref>https://coffeescript.org/ "CoffeeScript borrows chained comparisons from Python"</ref> [[Ruby (programming language)|Ruby]], [[YAML]]<ref name="smell">{{cite news |last1=Heller |first1=Martin |date=2011-10-18 |df=mdy |url=https://www.infoworld.com/article/2078452/turn-up-your-nose-at-dart-and-smell-the-coffeescript.html |title=Turn up your nose at Dart and smell the CoffeeScript |work=[[InfoWorld]] |access-date=2020-07-15}}</ref>

| influenced = [[MoonScript]], [[LiveScript (programming language)|LiveScript]], JavaScript

}}

'''CoffeeScript''' is a [[programming language]] that compiles to [[JavaScript]]. It adds [[syntactic sugar]] inspired by [[Ruby (programming language)|Ruby]], [[Python (programming language)|Python]], and [[Haskell (programming language)|Haskell]] in an effort to enhance JavaScript's brevity and readability.<ref name="thelittlebookoncoffeescriptLittleBookMacCaw">{{cite book |last1=MacCaw |first1=Alex |date=28 February 2012 |title=The Little Book on CoffeScriptCoffeeScript: |The author=AlexJavaScript MacCawDeveloper's Guide to Building Better Web Apps |edition=1st |publisher=[[O'Reilly Media]] |language=en |isbn=978-1-4493-2105-5}}</ref><ref name="LittleBookThomas">{{cite book |last1=Thomas |first1=Lucas |date=January2017 2012|title=The Little Book on CoffeeScript |edition=1st |publisher=CreateSpace Independent Publishing Platform |language=en |isbn=978-1-44935472-21051072-5}}</ref> SpecificSome additionaladded features include [[list comprehension]] and [[destructuring assignment]].

CoffeeScript support is included in [[Ruby on Rails]] version 3.1<ref>{{cite web |authorlast1=Peek |first1=Josh<!--ua ?--> Peek |url=https://twitter.com/joshpeek/status/58184348742074368 |title=Tweet by Rails Core Team Member |date= April 13, 2011}}</ref> and [[Play Framework]].<ref>{{Cite web |url=https://www.playframework.com/documentation/2.5.x/AssetsCoffeeScript |title=AssetsCoffeeScript - 2.5.x |website=www.playframework.com |access-date=2016-10-31}}</ref> In 2011, [[Brendan Eich]] referenced CoffeeScript as an influence on his thoughts about the future of JavaScript.<ref>Eich, Brendan. "[http://brendaneich.com/2011/01/harmony-of-my-dreams/ Harmony of My Dreams]"</ref><ref>Eich, Brendan. "[http://brendaneich.com/2011/05/my-jsconf-us-presentation/ My JSConf.US Presentation]"</ref>

== History ==

On December 13, 2009, [[Jeremy Ashkenas]] made the first [[Git (software)|Git]] commit of CoffeeScript with the comment: "initial commit of the mystery language"."<ref>Github. [https://github.com/jashkenas/coffee-script/commit/8e9d637985d2dc9b44922076ad54ffef7fa8e9c2 'initial commit of the mystery language']</ref> The compiler was written in Ruby. On December 24, he made the first tagged and documented release, 0.1.0. On February 21, 2010, he committed version 0.5, which replaced the Ruby compiler with a [[Self-hosting (compilers)|self-hosting]] version in pure CoffeeScript. By that time the project had attracted several other contributors on [[GitHub]], and was receiving over 300 page hits per day.

On December 24, 2010, Ashkenas announced the release of stable 1.0.0 to [[Hacker News]], the site where the project was announced for the first time.<ref>Hacker News. [https://news.ycombinator.com/item?id=2037801 CoffeeScript 1.0.0 announcement] posted by Jeremy Ashkenas on Dec 24, 2010</ref><ref>Hacker News. [https://news.ycombinator.com/item?id=1014080 Original CoffeeScript announcement] posted by Jeremy Ashkenas on Dec 24, 2009</ref>

On September 18, 2017, version 2.0.0 was introduced,<ref>coffeescript.org [http://coffeescript.org/announcing-coffeescript-2/ Announcing CoffeeScript 2]</ref> which "aims to bring CoffeeScript into the modern JavaScript era, closing gaps in compatibility with JavaScript while preserving the clean syntax that is CoffeeScript’sCoffeeScript's hallmark.".

== Syntax ==

Almost everything is an [[expression (computer science)|expression]] in CoffeeScript, for example, <code>if</code>, <code>switch</code> and <code>for</code> expressions (which have no return value in JavaScript) return a value. As in [[Perl]] and Ruby, these control statements also have postfix versions; for example, <code>if</code> can also be written in <code> consequent if condition</code> form.

Many unnecessary parentheses and braces can be omitted; for example, blocks of code can be denoted by indentation instead of braces, function calls are implicit, and object literals are often detected automatically.

To compute the [[body mass index]], one may do (here in [[JavaScript]]), one could write:

<syntaxhighlight lang="javascript">

constlet mass = 72;

constlet height = 1.78;

constlet BMI = mass / height ** 2;

if (18.5 <= BMI && BMI < 25) { alert('You are healthy!') };

</syntaxhighlight>

Line 50 ⟶ 55:

</syntaxhighlight>

To compute the [[greatest common divisor]] of two integers with the [[euclideanEuclidean algorithm]], in JavaScript one usually needs a ''while'' loop:{{Update inline|date=May 2021|reason=JavaScript also supports destructuring assignment}}

<syntaxhighlight lang="javascript">let gcd = (x, y) => {

gcd = (x, y) => {

do {

[x, y] = [y, x%y];

} while (y !== 0)

return x;

}</syntaxhighlight>

}

</syntaxhighlight>

Whereas in CoffeeScript one can use <code>until</code> and destructuring assignment<ref>CoffeeScript calls this "[[pattern matching]]", which is a non-standard use of that term.</ref> instead:

<syntaxhighlight lang="coffeescript">

gcd = (x, y) ->

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x

</syntaxhighlight>

Any ''for'' loop can be replaced by a [[list comprehension]]; so that to compute the squares of the positive odd numbers smaller than ten (i.e. numbers whose remainder modulo 2 is 1), one can do:

<syntaxhighlight lang="coffeescript">

alert n*n for n in [1..10] when n%2 is 1

</syntaxhighlight>

Alternatively, there is:

<syntaxhighlight lang="coffeescript">

alert n*n for n in [1..10] by 2

</syntaxhighlight>

A [[linear search]] can be implemented with a one-liner using the when keyword:

<syntaxhighlight lang="coffeescript">

names = ["Ivan", "Joanna", "Nikolay", "Mihaela"]

linearSearch = (searchName) -> alert(name) for name in names when name is searchName

</syntaxhighlight>

The <code>for ... in</code> syntax allows looping over arrays while the <code>for ... of</code> syntax allows looping over objects.

The <code>?</code> keyword quickly checks if a variable is <code>null</code> or <code>undefined</code> :

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This would alert "No person" if the variable is <code>null</code> or <code>undefined</code> and "Have person" if there is something there.

A common pre-[[ES6]] JavaScript snippet using the [[jQuery]] library is:

<syntaxhighlight lang="javascript">

$(document).ready(function() {

// Initialization code goes here

});

</syntaxhighlight>

Line 114 ⟶ 96:

$(function() {

// Initialization code goes here

});

</syntaxhighlight>

In CoffeeScript, the <code>function</code> keyword is replaced by the <code>-></code> symbol, and indentation is used instead of curly braces, as in other [[off-side rule]] languages such as Python and Haskell. Also, parentheses can usually be omitted, using indentation level instead to denote a function or block. Thus, the CoffeeScript equivalent of the snippet above is:

<!-- Ruby is probably the most similar language that GeSHi supports -->

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</syntaxhighlight>

Any [[For loop|''for'' loop]] can be replaced by a [[list comprehension]]; so that to compute the squares of the positive odd numbers smaller than ten (i.e. numbers whose remainder modulo 2 is 1), one can do:

CoffeeScript has been criticized for its unusual scoping

rules.<ref>{{cite web

<syntaxhighlight lang="coffeescript">

alert n*n for n in [1..10] when n%2 is 1

</syntaxhighlight>

Alternatively, there is:

<syntaxhighlight lang="coffeescript">

alert n*n for n in [1..10] by 2

</syntaxhighlight>

A [[linear search]] can be implemented with a one-liner using the when keyword:

<syntaxhighlight lang="coffeescript">

names = ["Ivan", "Joanna", "Nikolay", "Mihaela"]

linearSearch = (searchName) -> alert(name) for name in names when name is searchName

</syntaxhighlight>

The <code>for ... in</code> syntax allows looping over arrays while the <code>for ... of</code> syntax allows looping over objects.

CoffeeScript has been criticized for its unusual [[Scope (computer science)|scoping]] rules.<ref>{{cite web

|url=http://lucumr.pocoo.org/2011/12/22/implicit-scoping-in-coffeescript/

|title=The Problem with Implicit Scoping in CoffeeScript

Line 149 ⟶ 151:

|url=https://donatstudios.com/CoffeeScript-Madness

|title=CoffeeScript's Scoping is Madness

|date=25 July 2013

|access-date=2018-10-13

}}</ref> In particular, it completely disallows [[variable shadowing]] which makes reasoning about code more difficult and error-prone in some basic programming patterns established

by and taken for granted since [[procedural programming]] principles were defined.

error-prone in some basic programming patterns established

by and taken for granted since [[procedural programming]]

principles were defined.

For example, with the following code snippet in JavaScript

Line 163 ⟶ 164:

// ...

function baz() {

var foo = "bar";

console.log(`foo = ${foo}`);

}

// ...

Line 170 ⟶ 171:

</syntaxhighlight>

In CoffeeScript there is no way to tell if the scope of a variable is limited to a block or not without looking outside the block.

is limited to a block or not without looking outside the block.

== Development and distribution ==

The CoffeeScript compiler has been [[self-hosting (compilers)|self-hosting]] since version 0.5 and is available as a [[Node.js]] utility; however, the core compiler does not rely on Node.js and can be run in any [[JavaScript]] environment.<ref>[https://jashkenas.github.com/coffee-script/#installation CoffeeScript] {{webarchive|url=https://web.archive.org/web/20120427060308/http://jashkenas.github.com/coffee-script/ |date=2012-04-27 }}. Jashkenas.github.com. Retrieved on 2013-07-21.</ref> One alternative to the [[Node.js]] utility is the Coffee Maven Plugin, a plugin for the [[Apache Maven]] build system. The plugin uses the [[Rhino (JavaScript engine)|Rhino]] JavaScript engine written in [[Java (programming language)|Java]].{{citation needed|date=May 2019}}

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== Latest additions ==

{{uncited section|date=April 2024}}

* Source maps allow users to debug their CoffeeScript code directly, supporting CoffeeScript tracebacks on run time errors.

* CoffeeScript supports a form of [[Literateliterate Programmingprogramming]], using the <code>.coffee.md</code> or <code>.litcoffee</code> file extension. This allows CoffeeScriptthe [[source code]] to be written in [[Markdown]]. The compiler will treat any indented blocks (Markdown's way of indicating source code) as code, and ignore the rest as comments.

== Extensions ==

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== Adoption ==

On September 13, 2012, [[Dropbox (service)|Dropbox]] announced that their browser-side code base had been rewritten from [[JavaScript]] to CoffeeScript,<ref>{{cite web|url=https://tech.dropbox.comtech/?p=361application/dropbox-dives-into-coffeescript| title=Dropbox dives into CoffeeScript| date=13 September 2012|lastlast1= Wheeler| firstfirst1=Dan| last2= Mahkovec|first2= Ziga |last3= Varenhorst |first3=Chris|access-date=11 May 2013}}</ref> however it was migrated to [[TypeScript]] in 2017.<ref>{{cite web |last1=Goldstein |first1=David |title=The Great CoffeeScript to Typescript Migration of 2017 |url=https://dropbox.tech/frontend/the-great-coffeescript-to-typescript-migration-of-2017 |website=Dropbox.Tech |access-date=30 June 2020 |date=13 May 2020}}</ref>

[[GitHub]]'s internal style guide once said "write new JS in CoffeeScript", and whilethough it no longer does, all the advice in the style guide references how to write good CoffeeScript,<ref>{{cite web|url=https://github.com/styleguide/javascript|title=JavaScript · Styleguide · GitHub|publisher=Github.com|access-date=2015-11-30|archive-url=https://web.archive.org/web/20130815075924/https://github.com/styleguide/javascript|archive-date=2013-08-15|url-status=dead}}</ref> and theirits [[Atom (text editor)|Atom text editor]] was also written in the language, with configuration written in [[CSON]] ("CoffeeScript Object Notation"), a variant of [[JSON]].<ref>[{{cite web |url=https://github.com/atom/atom |title=Atom source code |publisher=[[GitHub]]. github|access-date=2021-06-26}}</ref><ref>{{cite web |title=Basic Customization |url=https://flight-manual.comatom-editor.cc/using-atom/sections/basic-customization/#configuring-with-cson Retrieved|website=[[Atom on(text 2021editor)|Atom]] Flight Manual |publisher=[[GitHub]] |access-06date=29 April 2024 |language=en |url-26status=live |archive-url=https://web.archive.org/web/20240429181349/https://flight-manual.atom-editor.cc/using-atom/sections/basic-customization/ |archive-date=2024-04-29}}</ref>

[[Pixel Game Maker MV]] makes uses of CoffeeScript as part of its game development environment.<ref name="CCG">{{cite web |last1=Cullen |first1=Daniel |title=PIXELPixel GAMEGame MAKERMaker MV (PC) |url=https://www.christcenteredgamer.com/reviews/pc-mac/7520-pixel-game-maker-mv-pc |website=Christ Centered Gaming |access-date=15 January 2021}}</ref>

== See also ==

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* [[Dart (programming language)]]

* [[Kotlin (programming language)]]

* [[LiveScript (programming language)]]

* [[Opa (programming language)]]

* [[Elm (programming language)]]

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== References ==

{{Reflist|30em}}

== Further reading ==

* {{Cite book |last1=Lee |first1=Patrick |date=May 14, 2014 |title=CoffeeScript in Action |edition=First1st |publisher=[[Manning Publications]] |page=432 |isbn=978-1617290626}}

* {{Cite journalbook |last1=Grosenbach |first1=Geoffrey |date=May 12, 2011 |title=Meet CoffeeScript |edition=First1st |publisher=[[PeepCode]]}}

* {{Cite book |last1=Bates |first1=Mark |date=May 31, 2012 |title=Programming in CoffeeScript |edition=First1st |publisher=[[Addison-Wesley]] |page=350 |isbn=978-0-321-82010-5}}

* {{Cite book |last1=MacCawBurnham |first1=AlexTrevor |date=JanuaryAugust 313, 20122011 |title=TheCoffeeScript: LittleAccelerated BookJavaScript onDevelopment CoffeeScript|edition=First1st |publisher=[[O'ReillyPragmatic MediaBookshelf]] |page=62[https://archive.org/details/isbn_9781934356784/page/138 138] |isbn=978-14493210551934356784 |url-access=registration |url=https://archive.org/details/isbn_9781934356784/page/138}}

* {{Cite book|last1=Burnham|first1=Trevor|date=August 3, 2011|title=CoffeeScript: Accelerated JavaScript Development|edition=First|publisher=[[Pragmatic Bookshelf]]|page=[https://archive.org/details/isbn_9781934356784/page/138 138]|isbn=978-1934356784|url-access=registration|url=https://archive.org/details/isbn_9781934356784/page/138}}

== External links ==

* {{Official website}}

{{Programming languages}}

{{JavaScript|state=collapsed}}

{{NodeJs}}

{{Programming languages}}

{{Authority control}}

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