jashkenas--coffeescript/documentation/sections/operators.md

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.

In a for loop, from compiles to the ES2015 of. (Yes, it’s unfortunate; the CoffeeScript of predates the ES2015 of.)

To simplify math expressions, ** can be used for exponentiation and // performs integer division. % works just like in JavaScript, while %% provides “dividend dependent modulo”:

codeFor('modulo')

All together now:

CoffeeScript	JavaScript
is	===
isnt	!==
not	!
and	&&
or	`
true, yes, on	true
false, no, off	false
@, this	this
a in b	[].indexOf.call(b, a) >= 0
a of b	a in b
for a from b	for (a of b)
a ** b	Math.pow(a, b)
a // b	Math.floor(a / b)
a %% b	(a % b + b) % b

codeFor('aliases')