I'm fairly excited about this direction for the language, and am looking
forward to writing (and more importantly, reading) more programs in this style.
More information about Literate CoffeeScript, including an
example program,
are available in this blog post.
Loops and Comprehensions
Most of the loops you'll write in CoffeeScript will be comprehensions
over arrays, objects, and ranges. Comprehensions replace (and compile into)
for loops, with optional guard clauses and the value of the current array index.
Unlike for loops, array comprehensions are expressions, and can be returned
and assigned.
# 吃午饭.
eat food for food in ['toast', 'cheese', 'wine']
# 精致的五道菜.
courses = ['greens', 'caviar', 'truffles', 'roast', 'cake']
menu i + 1, dish for dish, i in courses
# 注重健康的一餐.
foods = ['broccoli', 'spinach', 'chocolate']
eat food for food in foods when food isnt'chocolate'
Comprehensions should be able to handle most places where you otherwise
would use a loop, each/forEach, map, or select/filter, for example:
shortNames = (name for name in list when name.length < 5)
If you know the start and end of your loop, or would like to step through
in fixed-size increments, you can use a range to specify the start and
end of your comprehension.
countdown = (num for num in [10..1])
var countdown, num;
countdown = (function() {var _i, _results;
_results = [];
for (num = _i = 10; _i >= 1; num = --_i) {
_results.push(num);
}
return _results;
})();
load
run: countdown
Note how because we are assigning the value of the comprehensions to a
variable in the example above, CoffeeScript is collecting the result of
each iteration into an array. Sometimes functions end with loops that are
intended to run only for their side-effects. Be careful that you're not
accidentally returning the results of the comprehension in these cases,
by adding a meaningful return value — like true — or null,
to the bottom of your function.
To step through a range comprehension in fixed-size chunks,
use by, for example: evens = (x for x in [0..10] by 2)
Comprehensions can also be used to iterate over the keys and values in
an object. Use of to signal comprehension over the properties of
an object instead of the values in an array.
yearsOld = max: 10, ida: 9, tim: 11
ages = for child, age of yearsOld
"#{child} is #{age}"
var age, ages, child, yearsOld;
yearsOld = {
max: 10,
ida: 9,
tim: 11
};
ages = (function() {var _results;
_results = [];
for (child in yearsOld) {
age = yearsOld[child];
_results.push("" + child + " is " + age);
}
return _results;
})();
load
run: ages.join(", ")
If you would like to iterate over just the keys that are defined on the
object itself, by adding a hasOwnProperty
check to avoid properties that may be inherited from the prototype, use for own key, value of object
The only low-level loop that CoffeeScript provides is the while loop. The
main difference from JavaScript is that the while loop can be used
as an expression, returning an array containing the result of each iteration
through the loop.
# 经济 101ifthis.studyingEconomics
buy() while supply > demand
sell() until supply > demand
# 摇篮曲
num = 6
lyrics = while num -= 1"#{num} little monkeys, jumping on the bed.
One fell out and bumped his head."
var lyrics, num;
if (this.studyingEconomics) {
while (supply > demand) {
buy();
}
while (!(supply > demand)) {
sell();
}
}
num = 6;
lyrics = (function() {var _results;
_results = [];
while (num -= 1) {
_results.push("" + num + " little monkeys, jumping on the bed. One fell out and bumped his head.");
}
return _results;
})();
load
run: lyrics.join("
")
For readability, the until keyword is equivalent to while not,
and the loop keyword is equivalent to while true.
When using a JavaScript loop to generate functions, it's common to insert
a closure wrapper in order to ensure that loop variables are closed over,
and all the generated functions don't just share the final values. CoffeeScript
provides the do keyword, which immediately invokes a passed function,
forwarding any arguments.
for filename in list
do(filename) ->
fs.readFile filename, (err, contents) ->
compile filename, contents.toString()
Array Slicing and Splicing with Ranges
Ranges can also be used to extract slices of arrays.
With two dots (3..6), the range is inclusive (3, 4, 5, 6);
with three dots (3...6), the range excludes the end (3, 4, 5).
Slices indices have useful defaults. An omitted first index defaults to
zero and an omitted second index defaults to the size of the array.
Note that JavaScript strings are immutable, and can't be spliced.
Everything is an Expression (at least, as much as possible)
You might have noticed how even though we don't add return statements
to CoffeeScript functions, they nonetheless return their final value.
The CoffeeScript compiler tries to make sure that all statements in the
language can be used as expressions. Watch how the return gets
pushed down into each possible branch of execution in the function
below.
Even though functions will always return their final value, it's both possible
and encouraged to return early from a function body writing out the explicit
return (return value), when you know that you're done.
Because variable declarations occur at the top of scope, assignment can
be used within expressions, even for variables that haven't been seen before:
six = (one = 1) + (two = 2) + (three = 3)
var one, six, three, two;
six = (one = 1) + (two = 2) + (three = 3);
load
run: six
Things that would otherwise be statements in JavaScript, when used
as part of an expression in CoffeeScript, are converted into expressions
by wrapping them in a closure. This lets you do useful things, like assign
the result of a comprehension to a variable:
# 前十个全局属性(变量).
globals = (name for name ofwindow)[0...10]
var globals, name;
globals = ((function() {var _results;
_results = [];
for (name in window) {
_results.push(name);
}
return _results;
})()).slice(0, 10);
load
run: globals
As well as silly things, like passing a try/catch statement directly
into a function call:
alert(
try
nonexistent / undefinedcatch error
"And the error is ... #{error}"
)
var error;
alert((function() {try {
return nonexistent / void0;
} catch (_error) {
error = _error;
return"And the error is ... " + error;
}
})());
load
run
There are a handful of statements in JavaScript that can't be meaningfully
converted into expressions, namely break, continue,
and return. If you make use of them within a block of code,
CoffeeScript won't try to perform the conversion.
Operators and Aliases
Because the == operator frequently causes undesirable coercion,
is intransitive, and has a different meaning than in other languages,
CoffeeScript compiles == into ===, and != into
!==.
In addition, is compiles into ===,
and isnt into !==.
You can use not as an alias for !.
For logic, and compiles to &&, and or
into ||.
Instead of a newline or semicolon, then can be used to separate
conditions from expressions, in while,
if/else, and switch/when statements.
As in YAML, on and yes
are the same as boolean true, while off and no are boolean false.
unless can be used as the inverse of if.
As a shortcut for this.property, you can use @property.
You can use in to test for array presence, and of to
test for JavaScript object-key presence.
To simplify math expressions, ** can be used for exponentiation, // performs integer division and %% provides true mathematical modulo.
All together now:
CoffeeScript
JavaScript
is
===
isnt
!==
not
!
and
&&
or
||
true, yes, on
true
false, no, off
false
@, this
this
of
in
in
no JS equivalent
a ** b
Math.pow(a, b)
a // b
Math.floor(a / b)
a %% b
(a % b + b) % b
launch() if ignition ison
volume = 10if band isnt SpinalTap
letTheWildRumpusBegin() unless answer isnoif car.speed < limit then accelerate()
winner = yesif pick in [47, 92, 13]
print inspect "My name is #{@name}"
var volume, winner;
if (ignition === true) {
launch();
}
if (band !== SpinalTap) {
volume = 10;
}
if (answer !== false) {
letTheWildRumpusBegin();
}
if (car.speed < limit) {
accelerate();
}
if (pick === 47 || pick === 92 || pick === 13) {
winner = true;
}
print(inspect("My name is " + this.name));
load
The Existential Operator
It's a little difficult to check for the existence of a variable in
JavaScript. if (variable) ... comes close, but fails for zero,
the empty string, and false. CoffeeScript's existential operator ? returns true unless
a variable is null or undefined, which makes it analogous
to Ruby's nil?
It can also be used for safer conditional assignment than ||=
provides, for cases where you may be handling numbers or strings.
var footprints, solipsism, speed;
if ((typeof mind !== "undefined" && mind !== null) && (typeof world === "undefined" || world === null)) {
solipsism = true;
}
speed = 0;
if (speed == null) {
speed = 15;
}
footprints = typeof yeti !== "undefined" && yeti !== null ? yeti : "bear";
load
run: footprints
The accessor variant of the existential operator ?. can be used to soak
up null references in a chain of properties. Use it instead
of the dot accessor . in cases where the base value may be null
or undefined. If all of the properties exist then you'll get the expected
result, if the chain is broken, undefined is returned instead of
the TypeError that would be raised otherwise.
Classes, Inheritance, and Super
JavaScript's prototypal inheritance has always been a bit of a
brain-bender, with a whole family tree of libraries that provide a cleaner
syntax for classical inheritance on top of JavaScript's prototypes:
Base2,
Prototype.js,
JS.Class, etc.
The libraries provide syntactic sugar, but the built-in inheritance would
be completely usable if it weren't for a couple of small exceptions:
it's awkward to call super (the prototype object's
implementation of the current function), and it's awkward to correctly
set the prototype chain.
Instead of repetitively attaching functions to a prototype, CoffeeScript
provides a basic class structure that allows you to name your class,
set the superclass, assign prototypal properties, and define the constructor,
in a single assignable expression.
Constructor functions are named, to better support helpful stack traces.
In the first class in the example below, this.constructor.name is "Animal".
classAnimalconstructor: (@name) ->move: (meters) ->
alert @name + " moved #{meters}m."classSnakeextendsAnimalmove: ->
alert "Slithering..."super5classHorseextendsAnimalmove: ->
alert "Galloping..."super45
sam = new Snake "Sammy the Python"
tom = new Horse "Tommy the Palomino"
sam.move()
tom.move()
If structuring your prototypes classically isn't your cup of tea, CoffeeScript
provides a couple of lower-level conveniences. The extends operator
helps with proper prototype setup, and can be used to create an inheritance
chain between any pair of constructor functions; :: gives you
quick access to an object's prototype; and super()
is converted into a call against the immediate ancestor's method of the same name.
Finally, class definitions are blocks of executable code, which make for interesting
metaprogramming possibilities. Because in the context of a class definition,
this is the class object itself (the constructor function), you
can assign static properties by using @property: value, and call
functions defined in parent classes: @attr 'title', type: 'text'
Destructuring Assignment
To make extracting values from complex arrays and objects more convenient,
CoffeeScript implements ECMAScript Harmony's proposed
destructuring assignment
syntax. When you assign an array or object literal to a value, CoffeeScript
breaks up and matches both sides against each other, assigning the values
on the right to the variables on the left. In the simplest case, it can be
used for parallel assignment:
var city, futurists, name, street, _ref, _ref1;
futurists = {
sculptor: "Umberto Boccioni",
painter: "Vladimir Burliuk",
poet: {
name: "F.T. Marinetti",
address: ["Via Roma 42R", "Bellagio, Italy 22021"]
}
};
_ref = futurists.poet, name = _ref.name, (_ref1 = _ref.address, street = _ref1[0], city = _ref1[1]);
load
run: "name + "-" + street"
Destructuring assignment can even be combined with splats.
tag = "<impossible>"
[open, contents..., close] = tag.split("")
var close, contents, open, tag, _i, _ref,
__slice = [].slice;
tag = "<impossible>";
_ref = tag.split(""), open = _ref[0], contents = 3 <= _ref.length ? __slice.call(_ref, 1, _i = _ref.length - 1) : (_i = 1, []), close = _ref[_i++];
load
run: contents.join("")
Expansion can be used to retrieve elements from the end of an array without having to assign the rest of its values. It works in function parameter lists as well.
text = "Every literary critic believes he will
outwit history and have the last word"
[first, ..., last] = text.split " "
var first, last, text, _ref;
text = "Every literary critic believes he will outwit history and have the last word";
_ref = text.split(" "), first = _ref[0], last = _ref[_ref.length - 1];
load
run: "first + " " + last"
Destructuring assignment is also useful when combined with class constructors
to assign properties to your instance from an options object passed to the constructor.
classPersonconstructor: (options) ->
{@name, @age, @height} = options
tim = new Person age: 4
var Person, tim;
Person = (function() {functionPerson(options) {this.name = options.name, this.age = options.age, this.height = options.height;
}
return Person;
})();
tim = new Person({
age: 4
});
load
run: tim.age
Function binding
In JavaScript, the this keyword is dynamically scoped to mean the
object that the current function is attached to. If you pass a function as
a callback or attach it to a different object, the original value of this
will be lost. If you're not familiar with this behavior,
this Digital Web article
gives a good overview of the quirks.
The fat arrow => can be used to both define a function, and to bind
it to the current value of this, right on the spot. This is helpful
when using callback-based libraries like Prototype or jQuery, for creating
iterator functions to pass to each, or event-handler functions
to use with bind. Functions created with the fat arrow are able to access
properties of the this where they're defined.
If we had used -> in the callback above, @customer would
have referred to the undefined "customer" property of the DOM element,
and trying to call purchase() on it would have raised an exception.
When used in a class definition, methods declared with the fat arrow will
be automatically bound to each instance of the class when the instance is
constructed.
Embedded JavaScript
Hopefully, you'll never need to use it, but if you ever need to intersperse
snippets of JavaScript within your CoffeeScript, you can
use backticks to pass it straight through.
hi = `function() {return [document.title, "Hello JavaScript"].join(": ");
}`
var hi;
hi = function() {return [document.title, "Hello JavaScript"].join(": ");
};
load
run: hi()
Switch/When/ElseSwitch statements in JavaScript are a bit awkward. You need to
remember to break at the end of every case statement to
avoid accidentally falling through to the default case.
CoffeeScript prevents accidental fall-through, and can convert the switch
into a returnable, assignable expression. The format is: switch condition,
when clauses, else the default case.
As in Ruby, switch statements in CoffeeScript can take multiple
values for each when clause. If any of the values match, the clause
runs.
switch day
when"Mon"then go work
when"Tue"then go relax
when"Thu"then go iceFishing
when"Fri", "Sat"if day is bingoDay
go bingo
go dancing
when"Sun"then go church
else go work
String Interpolation, Block Strings, and Block Comments
Ruby-style string interpolation is included in CoffeeScript. Double-quoted
strings allow for interpolated values, using #{ ... },
and single-quoted strings are literal.
author = "Wittgenstein"
quote = "A picture is a fact. -- #{ author }"
sentence = "#{ 22 / 7 } is a decent approximation of π"
var author, quote, sentence;
author = "Wittgenstein";
quote = "A picture is a fact. -- " + author;
sentence = "" + (22 / 7) + " is a decent approximation of π";
load
run: sentence
Multiline strings are allowed in CoffeeScript. Lines are joined by a single space unless they end with a backslash. Indentation is ignored.
mobyDick = "Call me Ishmael. Some years ago --
never mind how long precisely -- having little
or no money in my purse, and nothing particular
to interest me on shore, I thought I would sail
about a little and see the watery part of the
world..."
var mobyDick;
mobyDick = "Call me Ishmael. Some years ago -- never mind how long precisely -- having little or no money in my purse, and nothing particular to interest me on shore, I thought I would sail about a little and see the watery part of the world...";
load
run: mobyDick
Block strings can be used to hold formatted or indentation-sensitive text
(or, if you just don't feel like escaping quotes and apostrophes). The
indentation level that begins the block is maintained throughout, so
you can keep it all aligned with the body of your code.
html = """
<strong>
cup of coffeescript
</strong>
"""
var html;
html = "<strong>\n cup of coffeescript\n</strong>";
load
run: html
Double-quoted block strings, like other double-quoted strings, allow interpolation.
Sometimes you'd like to pass a block comment through to the generated
JavaScript. For example, when you need to embed a licensing header at
the top of a file. Block comments, which mirror the syntax for block strings,
are preserved in the generated code.
###
SkinnyMochaHalfCaffScript Compiler v1.0
Released under the MIT License
###
/*
SkinnyMochaHalfCaffScript Compiler v1.0
Released under the MIT License
*/
load
Block Regular Expressions
Similar to block strings and comments, CoffeeScript supports block regexes —
extended regular expressions that ignore internal whitespace and can contain
comments and interpolation. Modeled after Perl's /x modifier, CoffeeScript's
block regexes are delimited by /// and go a long way towards making complex
regular expressions readable. To quote from the CoffeeScript source:
var OPERATOR;
OPERATOR = /^(?:[-=]>|[-+*\/%<>&|^!?=]=|>>>=?|([-+:])\1|([&|<>])\2=?|\?\.|\.{2,3})/;
load
Cake, and Cakefiles
CoffeeScript includes a (very) simple build system similar to
Make and
Rake. Naturally,
it's called Cake, and is used for the tasks that build and test the CoffeeScript
language itself. Tasks are defined in a file named Cakefile, and
can be invoked by running cake [task] from within the directory.
To print a list of all the tasks and options, just type cake.
Task definitions are written in CoffeeScript, so you can put arbitrary code
in your Cakefile. Define a task with a name, a long description, and the
function to invoke when the task is run. If your task takes a command-line
option, you can define the option with short and long flags, and it will
be made available in the options object. Here's a task that uses
the Node.js API to rebuild CoffeeScript's parser:
fs = require'fs'
option '-o', '--output [DIR]', 'directory for compiled code'
task 'build:parser', 'rebuild the Jison parser', (options) ->require'jison'
code = require('./lib/grammar').parser.generate()
dir = options.output or'lib'
fs.writeFile "#{dir}/parser.js", code
var fs;
fs = require('fs');
option('-o', '--output [DIR]', 'directory for compiled code');
task('build:parser', 'rebuild the Jison parser', function(options) {var code, dir;
require('jison');
code = require('./lib/grammar').parser.generate();
dir = options.output || 'lib';
return fs.writeFile("" + dir + "/parser.js", code);
});
load
If you need to invoke one task before another — for example, running
build before test, you can use the invoke function:
invoke 'build'. Cake tasks are a minimal way to expose your
CoffeeScript functions to the command line, so
don't expect any fanciness built-in.
If you need dependencies, or async callbacks, it's best to put them in your
code itself — not the cake task.
Source Maps
CoffeeScript 1.6.1 and above include support for generating source maps,
a way to tell your JavaScript engine what part of your CoffeeScript
program matches up with the code being evaluated. Browsers that support it
can automatically use source maps to show your original source code
in the debugger. To generate source maps alongside your JavaScript files,
pass the --map or -m flag to the compiler.
For a full introduction to source maps, how they work, and how to hook
them up in your browser, read the
HTML5 Tutorial.
"text/coffeescript" Script Tags
While it's not recommended for serious use, CoffeeScripts may be included
directly within the browser using <script type="text/coffeescript">
tags. The source includes a compressed and minified version of the compiler
(Download current version here, 39k when gzipped)
as extras/coffee-script.js. Include this file on a page with
inline CoffeeScript tags, and it will compile and evaluate them in order.
In fact, the little bit of glue script that runs "Try CoffeeScript" above,
as well as the jQuery for the menu, is implemented in just this way.
View source and look at the bottom of the page to see the example.
Including the script also gives you access to CoffeeScript.compile()
so you can pop open Firebug and try compiling some strings.
The usual caveats about CoffeeScript apply — your inline scripts will
run within a closure wrapper, so if you want to expose global variables or
functions, attach them to the window object.
Books
There are a number of excellent resources to help you get
started with CoffeeScript, some of which are freely available online.
Smooth CoffeeScript
is a reimagination of the excellent book
Eloquent JavaScript, as if
it had been written in CoffeeScript instead. Covers language features
as well as the functional and object oriented programming styles. By
E. Hoigaard.
CoffeeScript: Accelerated JavaScript Development
is Trevor Burnham's thorough
introduction to the language. By the end of the book, you'll have built
a fast-paced multiplayer word game, writing both the client-side and Node.js
portions in CoffeeScript.
CoffeeScript Ristretto
is a deep dive into CoffeeScript's semantics from simple functions up through
closures, higher-order functions, objects, classes, combinators, and decorators.
By Reg Braithwaite.
Testing with CoffeeScript
is a succinct and freely downloadable guide to building testable
applications with CoffeeScript and Jasmine.
CoffeeScript Application Development
is a new book from Packt Publishing that introduces CoffeeScript while
walking through the process of building a demonstration web application.
CoffeeScript in Action
is a new book from Manning Publications that covers CoffeeScript syntax, composition techniques
and application development.
Meet CoffeeScript
is a 75-minute long screencast by PeepCode.
Highly memorable for its animations which demonstrate transforming CoffeeScript
into the equivalent JS.
If you're looking for less of a time commitment, RailsCasts'
CoffeeScript Basics
should have you covered, hitting all of the important notes about CoffeeScript
in 11 minutes.
Source Code
Use bin/coffee to test your changes, bin/cake test to run the test suite, bin/cake build to rebuild the CoffeeScript compiler, and bin/cake build:parser to regenerate the Jison parser if you're
working on the grammar.
git checkout lib && bin/cake build:full is a good command to run when you're working
on the core language. It'll refresh the lib directory
(in case you broke something), build your altered compiler, use that to
rebuild itself (a good sanity test) and then run all of the tests. If
they pass, there's a good chance you've made a successful change.
CoffeeScript Issues
Bug reports, feature proposals, and ideas for changes to the language belong here.
CoffeeScript Google Group
If you'd like to ask a question, the mailing list is a good place to get help.
The FAQ
Perhaps your CoffeeScript-related question has been asked before. Check the FAQ first.
JS2Coffee
Is a very well done reverse JavaScript-to-CoffeeScript compiler. It's
not going to be perfect (infer what your JavaScript classes are, when
you need bound functions, and so on...) — but it's a great starting
point for converting simple scripts.
High-Rez Logo
The CoffeeScript logo is available in Illustrator, EPS and PSD formats, for use
in presentations.
Web Chat (IRC)
Quick help and advice can usually be found in the CoffeeScript IRC room.
Join #coffeescript on irc.freenode.net, or click the
button below to open a webchat session on this page.
When requiring CoffeeScript files in Node you must now explicitly register the compiler. This can be done with require 'coffee-script/register' or CoffeeScript.register(). Also for configuration such as Mocha's, use coffee-script/register.
Improved error messages, source maps and stack traces. Source maps now use the updated //# syntax.
Leading . now closes all open calls, allowing for simpler chaining syntax.
Added **, // and %% operators and ... expansion in parameter lists and destructuring expressions.
Multiline strings are now joined by a single space and ignore all indentation. A backslash at the end of a line can denote the amount of whitespace between lines, in both strings and heredocs. Backslashes correctly escape whitespace in block regexes.
Closing brackets can now be indented and therefore no longer cause unexpected error.
Several breaking compilation fixes. Non-callable literals (strings, numbers etc.) don't compile in a call now and multiple postfix conditionals compile properly. Postfix conditionals and loops always bind object literals. Conditional assignment compiles properly in subexpressions. super is disallowed outside of methods and works correctly inside for loops.
Formatting of compiled block comments has been improved.
No more -p folders on Windows.
The options object passed to CoffeeScript is no longer mutated.
The CoffeeScript REPL now remembers your history between sessions.
Just like a proper REPL should.
You can now use require in Node to load .coffee.md
Literate CoffeeScript files. In the browser,
text/literate-coffeescript script tags.
The old coffee --lint command has been removed. It was useful
while originally working on the compiler, but has been surpassed by
JSHint. You may now use -l to pass literate files in over
stdio.
Bugfixes for Windows path separators, catch without naming
the error, and executable-class-bodies-with-
prototypal-property-attachment.
Source maps have been used to provide automatic line-mapping when
running CoffeeScript directly via the coffee command, and
for automatic line-mapping when running CoffeeScript directly in the
browser. Also, to provide better error messages for semantic errors
thrown by the compiler —
with colors, even.
Improved support for mixed literate/vanilla-style CoffeeScript projects,
and generating source maps for both at the same time.
Fixes for 1.6.x regressions with overriding inherited bound
functions, and for Windows file path management.
The coffee command can now correctly fork()
both .coffee and .js files. (Requires Node.js 0.9+)
First release of source maps. Pass the
--map flag to the compiler, and off you go. Direct all your
thanks over to Jason Walton.
Fixed a 1.5.0 regression with multiple implicit calls against an
indented implicit object. Combinations of implicit function calls
and implicit objects should generally be parsed better now —
but it still isn't good style to nest them too heavily.
.coffee.md is now also supported as a Literate CoffeeScript
file extension, for existing tooling.
.litcoffee remains the canonical one.
Several minor fixes surrounding member properties, bound methods and
super in class declarations.
Due to the new semantics of JavaScript's strict mode, CoffeeScript no
longer guarantees that constructor functions have names in all runtimes.
See #2052
for discussion.
Inside of a nested function inside of an instance method, it's now possible
to call super more reliably (walks recursively up).
Named loop variables no longer have different scoping heuristics than
other local variables. (Reverts #643)
Fix for splats nested within the LHS of destructuring assignment.
Corrections to our compile time strict mode forbidding of octal literals.
CoffeeScript now enforces all of JavaScript's Strict Mode early syntax
errors at compile time. This includes old-style octal literals,
duplicate property names in object literals, duplicate parameters in
a function definition, deleting naked variables, setting the value of
eval or arguments, and more.
See a full discussion at
#1547.
The REPL now has a handy new multi-line mode for entering large
blocks of code. It's useful when copy-and-pasting examples into the
REPL. Enter multi-line mode with Ctrl-V. You may also now
pipe input directly into the REPL.
CoffeeScript now prints a Generated by CoffeeScript VERSION
header at the top of each compiled file.
Conditional assignment of previously undefined variables
a or= b is now considered a syntax error.
A tweak to the semantics of do, which can now be used to
more easily simulate a namespace: do (x = 1, y = 2) -> ...
Loop indices are now mutable within a loop iteration, and immutable
between them.
Both endpoints of a slice are now allowed to be omitted for consistency,
effectively creating a shallow copy of the list.
Additional tweaks and improvments to coffee --watch under
Node's "new" file watching API. Watch will now beep by default
if you introduce a syntax error into a watched script. We also now
ignore hidden directories by default when watching recursively.
Multiple improvements to coffee --watch and --join.
You may now use both together, as well as add and remove
files and directories within a --watch'd folder.
The throw statement can now be used as part of an expression.
Block comments at the top of the file will now appear outside of the
safety closure wrapper.
Fixed a number of minor 1.1.3 regressions having to do with trailing
operators and unfinished lines, and a more major 1.1.3 regression that
caused bound functions within bound class functions to have the incorrect
this.
Ahh, whitespace. CoffeeScript's compiled JS now tries to space things
out and keep it readable, as you can see in the examples on this page.
You can now call super in class level methods in class bodies,
and bound class methods now preserve their correct context.
JavaScript has always supported octal numbers 010 is 8,
and hexadecimal numbers 0xf is 15, but CoffeeScript now
also supports binary numbers: 0b10 is 2.
The CoffeeScript module has been nested under a subdirectory to make
it easier to require individual components separately, without
having to use npm. For example, after adding the CoffeeScript
folder to your path: require('coffee-script/lexer')
There's a new "link" feature in Try CoffeeScript on this webpage. Use
it to get a shareable permalink for your example script.
The coffee --watch feature now only works on Node.js 0.6.0
and higher, but now also works properly on Windows.
1.1.2 – August 4, 2011
Fixes for block comment formatting, ?= compilation, implicit calls
against control structures, implicit invocation of a try/catch block,
variadic arguments leaking from local scope, line numbers in syntax errors
following heregexes, property access on parenthesized number literals,
bound class methods and super with reserved names, a REPL overhaul,
consecutive compiled semicolons, block comments in implicitly called objects,
and a Chrome bug.
1.1.1
– May 10, 2011
Bugfix release for classes with external constructor functions, see
issue #1182.
1.1.0
– May 1, 2011
When running via the coffee executable, process.argv and
friends now report coffee instead of node.
Better compatibility with Node.js 0.4.x module lookup changes.
The output in the REPL is now colorized, like Node's is.
Giving your concatenated CoffeeScripts a name when using --join is now mandatory.
Fix for lexing compound division /= as a regex accidentally.
All text/coffeescript tags should now execute in the order they're included.
Fixed an issue with extended subclasses using external constructor functions.
Fixed an edge-case infinite loop in addImplicitParentheses.
Fixed exponential slowdown with long chains of function calls.
Globals no longer leak into the CoffeeScript REPL.
Splatted parameters are declared local to the function.
1.0.1
– Jan 31, 2011
Fixed a lexer bug with Unicode identifiers. Updated REPL for compatibility
with Node.js 0.3.7. Fixed requiring relative paths in the REPL. Trailing
return and return undefined are now optimized away.
Stopped requiring the core Node.js "util" module for
back-compatibility with Node.js 0.2.5. Fixed a case where a
conditional return would cause fallthrough in a switch
statement. Optimized empty objects in destructuring assignment.
1.0.0
– Dec 24, 2010
CoffeeScript loops no longer try to preserve block scope when functions
are being generated within the loop body. Instead, you can use the
do keyword to create a convenient closure wrapper.
Added a --nodejs flag for passing through options directly
to the node executable.
Better behavior around the use of pure statements within expressions.
Fixed inclusive slicing through -1, for all browsers, and splicing
with arbitrary expressions as endpoints.
0.9.6
– Dec 6, 2010
The REPL now properly formats stacktraces, and stays alive through
asynchronous exceptions. Using --watch now prints timestamps as
files are compiled. Fixed some accidentally-leaking variables within
plucked closure-loops. Constructors now maintain their declaration
location within a class body. Dynamic object keys were removed.
Nested classes are now supported. Fixes execution context for naked
splatted functions. Bugfix for inversion of chained comparisons.
Chained class instantiation now works properly with splats.
0.9.5
– Nov 21, 2010
0.9.5 should be considered the first release candidate for CoffeeScript 1.0.
There have been a large number of internal changes since the previous release,
many contributed from satyr's Coco
dialect of CoffeeScript. Heregexes (extended regexes) were added. Functions
can now have default arguments. Class bodies are now executable code.
Improved syntax errors for invalid CoffeeScript. undefined now
works like null, and cannot be assigned a new value.
There was a precedence change with respect to single-line comprehensions:
result = i for i in list used to parse as result = (i for i in list)
by default ... it now parses as (result = i) for i in list.
0.9.4
– Sep 21, 2010
CoffeeScript now uses appropriately-named temporary variables, and recycles
their references after use. Added require.extensions support for
Node.js 0.3. Loading CoffeeScript in the browser now adds just a
single CoffeeScript object to global scope.
Fixes for implicit object and block comment edge cases.
0.9.3
– Sep 16, 2010
CoffeeScript switch statements now compile into JS switch
statements — they previously compiled into if/else chains
for JavaScript 1.3 compatibility.
Soaking a function invocation is now supported. Users of the RubyMine
editor should now be able to use --watch mode.
0.9.2
– Aug 23, 2010
Specifying the start and end of a range literal is now optional, eg. array[3..].
You can now say a not instanceof b.
Fixed important bugs with nested significant and non-significant indentation (Issue #637).
Added a --require flag that allows you to hook into the coffee command.
Added a custom jsl.conf file for our preferred JavaScriptLint setup.
Sped up Jison grammar compilation time by flattening rules for operations.
Block comments can now be used with JavaScript-minifier-friendly syntax.
Added JavaScript's compound assignment bitwise operators. Bugfixes to
implicit object literals with leading number and string keys, as the subject
of implicit calls, and as part of compound assignment.
0.9.1
– Aug 11, 2010
Bugfix release for 0.9.1. Greatly improves the handling of mixed
implicit objects, implicit function calls, and implicit indentation.
String and regex interpolation is now strictly #{ ... } (Ruby style).
The compiler now takes a --require flag, which specifies scripts
to run before compilation.
0.9.0
– Aug 4, 2010
The CoffeeScript 0.9 series is considered to be a release candidate
for 1.0; let's give her a shakedown cruise. 0.9.0 introduces a massive
backwards-incompatible change: Assignment now uses =, and object
literals use :, as in JavaScript. This allows us to have implicit
object literals, and YAML-style object definitions. Half assignments are
removed, in favor of +=, or=, and friends.
Interpolation now uses a hash mark # instead of the dollar sign
$ — because dollar signs may be part of a valid JS identifier.
Downwards range comprehensions are now safe again, and are optimized to
straight for loops when created with integer endpoints.
A fast, unguarded form of object comprehension was added:
for all key, value of object. Mentioning the super keyword
with no arguments now forwards all arguments passed to the function,
as in Ruby. If you extend class B from parent class A, if
A has an extended method defined, it will be called, passing in B —
this enables static inheritance, among other things. Cleaner output for
functions bound with the fat arrow. @variables can now be used
in parameter lists, with the parameter being automatically set as a property
on the object — useful in constructors and setter functions.
Constructor functions can now take splats.
0.7.2
– Jul 12, 2010
Quick bugfix (right after 0.7.1) for a problem that prevented coffee
command-line options from being parsed in some circumstances.
0.7.1
– Jul 11, 2010
Block-style comments are now passed through and printed as JavaScript block
comments -- making them useful for licenses and copyright headers. Better
support for running coffee scripts standalone via hashbangs.
Improved syntax errors for tokens that are not in the grammar.
0.7.0
– Jun 28, 2010
Official CoffeeScript variable style is now camelCase, as in JavaScript.
Reserved words are now allowed as object keys, and will be quoted for you.
Range comprehensions now generate cleaner code, but you have to specify by -1
if you'd like to iterate downward. Reporting of syntax errors is greatly
improved from the previous release. Running coffee with no arguments
now launches the REPL, with Readline support. The <- bind operator
has been removed from CoffeeScript. The loop keyword was added,
which is equivalent to a while true loop. Comprehensions that contain
closures will now close over their variables, like the semantics of a forEach.
You can now use bound function in class definitions (bound to the instance).
For consistency, a in b is now an array presence check, and a of b
is an object-key check. Comments are no longer passed through to the generated
JavaScript.
0.6.2
– May 15, 2010
The coffee command will now preserve directory structure when
compiling a directory full of scripts. Fixed two omissions that were preventing
the CoffeeScript compiler from running live within Internet Explorer.
There's now a syntax for block comments, similar in spirit to CoffeeScript's heredocs.
ECMA Harmony DRY-style pattern matching is now supported, where the name
of the property is the same as the name of the value: {name, length}: func.
Pattern matching is now allowed within comprehension variables. unless
is now allowed in block form. until loops were added, as the inverse
of while loops. switch statements are now allowed without
switch object clauses. Compatible
with Node.js v0.1.95.
0.6.1
– Apr 12, 2010
Upgraded CoffeeScript for compatibility with the new Node.js v0.1.90
series.
0.6.0
– Apr 3, 2010
Trailing commas are now allowed, a-la Python. Static
properties may be assigned directly within class definitions,
using @property notation.
0.5.6
– Mar 23, 2010
Interpolation can now be used within regular expressions and heredocs, as well as
strings. Added the <- bind operator.
Allowing assignment to half-expressions instead of special ||=-style
operators. The arguments object is no longer automatically converted into
an array. After requiring coffee-script, Node.js can now directly
load .coffee files, thanks to registerExtension. Multiple
splats can now be used in function calls, arrays, and pattern matching.
0.5.5
– Mar 8, 2010
String interpolation, contributed by
Stan Angeloff.
Since --run has been the default since 0.5.3, updating
--stdio and --eval to run by default, pass --compile
as well if you'd like to print the result.
0.5.4
– Mar 3, 2010
Bugfix that corrects the Node.js global constants __filename and
__dirname. Tweaks for more flexible parsing of nested function
literals and improperly-indented comments. Updates for the latest Node.js API.
0.5.3
– Feb 27, 2010
CoffeeScript now has a syntax for defining classes. Many of the core
components (Nodes, Lexer, Rewriter, Scope, Optparse) are using them.
Cakefiles can use optparse.coffee to define options for tasks.
--run is now the default flag for the coffee command,
use --compile to save JavaScripts. Bugfix for an ambiguity between
RegExp literals and chained divisions.
0.5.2
– Feb 25, 2010
Added a compressed version of the compiler for inclusion in web pages as
extras/coffee-script.js. It'll automatically run any script tags
with type text/coffeescript for you. Added a --stdio option
to the coffee command, for piped-in compiles.
0.5.1
– Feb 24, 2010
Improvements to null soaking with the existential operator, including
soaks on indexed properties. Added conditions to while loops,
so you can use them as filters with when, in the same manner as
comprehensions.
0.5.0
– Feb 21, 2010
CoffeeScript 0.5.0 is a major release, While there are no language changes,
the Ruby compiler has been removed in favor of a self-hosting
compiler written in pure CoffeeScript.
0.3.2
– Feb 8, 2010@property is now a shorthand for this.property.
Switched the default JavaScript engine from Narwhal to Node.js. Pass
the --narwhal flag if you'd like to continue using it.
0.3.0
– Jan 26, 2010
CoffeeScript 0.3 includes major syntax changes:
The function symbol was changed to
->, and the bound function symbol is now =>.
Parameter lists in function definitions must now be wrapped in parentheses.
Added property soaking, with the ?. operator.
Made parentheses optional, when invoking functions with arguments.
Removed the obsolete block literal syntax.
0.2.6
– Jan 17, 2010
Added Python-style chained comparisons, the conditional existence
operator ?=, and some examples from Beautiful Code.
Bugfixes relating to statement-to-expression conversion, arguments-to-array
conversion, and the TextMate syntax highlighter.
0.2.5
– Jan 13, 2010
The conditions in switch statements can now take multiple values at once —
If any of them are true, the case will run. Added the long arrow ==>,
which defines and immediately binds a function to this. While loops can
now be used as expressions, in the same way that comprehensions can. Splats
can be used within pattern matches to soak up the rest of an array.
0.2.4
– Jan 12, 2010
Added ECMAScript Harmony style destructuring assignment, for dealing with
extracting values from nested arrays and objects. Added indentation-sensitive
heredocs for nicely formatted strings or chunks of code.
0.2.3
– Jan 11, 2010
Axed the unsatisfactory ino keyword, replacing it with of for
object comprehensions. They now look like: for prop, value of object.
0.2.2
– Jan 10, 2010
When performing a comprehension over an object, use ino, instead
of in, which helps us generate smaller, more efficient code at
compile time.
Added :: as a shorthand for saying .prototype.
The "splat" symbol has been changed from a prefix asterisk *, to
a postfix ellipsis ...
Added JavaScript's in operator,
empty return statements, and empty while loops.
Constructor functions that start with capital letters now include a
safety check to make sure that the new instance of the object is returned.
The extends keyword now functions identically to goog.inherits
in Google's Closure Library.
0.2.1
– Jan 5, 2010
Arguments objects are now converted into real arrays when referenced.
0.2.0
– Jan 5, 2010
Major release. Significant whitespace. Better statement-to-expression
conversion. Splats. Splice literals. Object comprehensions. Blocks.
The existential operator. Many thanks to all the folks who posted issues,
with special thanks to
Liam O'Connor-Davis for whitespace
and expression help.
0.1.6
– Dec 27, 2009
Bugfix for running coffee --interactive and --run
from outside of the CoffeeScript directory. Bugfix for nested
function/if-statements.
0.1.5
– Dec 26, 2009
Array slice literals and array comprehensions can now both take Ruby-style
ranges to specify the start and end. JavaScript variable declaration is
now pushed up to the top of the scope, making all assignment statements into
expressions. You can use \ to escape newlines.
The coffee-script command is now called coffee.
0.1.4
– Dec 25, 2009
The official CoffeeScript extension is now .coffee instead of
.cs, which properly belongs to
C#.
Due to popular demand, you can now also use = to assign. Unlike
JavaScript, = can also be used within object literals, interchangeably
with :. Made a grammatical fix for chained function calls
like func(1)(2)(3)(4). Inheritance and super no longer use
__proto__, so they should be IE-compatible now.
0.1.3
– Dec 25, 2009
The coffee command now includes --interactive,
which launches an interactive CoffeeScript session, and --run,
which directly compiles and executes a script. Both options depend on a
working installation of Narwhal.
The aint keyword has been replaced by isnt, which goes
together a little smoother with is.
Quoted strings are now allowed as identifiers within object literals: eg.
{"5+5": 10}.
All assignment operators now use a colon: +:, -:,
*:, etc.
0.1.2
– Dec 24, 2009
Fixed a bug with calling super() through more than one level of
inheritance, with the re-addition of the extends keyword.
Added experimental Narwhal
support (as a Tusk package), contributed by
Tom Robinson, including
bin/cs as a CoffeeScript REPL and interpreter.
New --no-wrap option to suppress the safety function
wrapper.
0.1.1
– Dec 24, 2009
Added instanceof and typeof as operators.
0.1.0
– Dec 24, 2009
Initial CoffeeScript release.
