== 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 !==.not as an alias for !.and compiles to &&, and or into ||.while, if/else, and switch/when statements.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.in to test for array presence, and of to test for JavaScript object-key presence.for loop, from compiles to the ES2015 of. (Yes, it’s unfortunate; the CoffeeScript of predates the ES2015 of.)** can be used for exponentiation and // performs floor division. % works just like in JavaScript, while %% provides “dividend dependent modulo”:-7 % 5 == -2 # The remainder of 7 / 5
-7 %% 5 == 3 # n %% 5 is always between 0 and 4
tabs.selectTabAtIndex((tabs.currentIndex - count) %% tabs.length)
var modulo = function(a, b) { return (+a % (b = +b) + b) % b; };
-7 % 5 === -2; // The remainder of 7 / 5
modulo(-7, 5) === 3; // n %% 5 is always between 0 and 4
tabs.selectTabAtIndex(modulo(tabs.currentIndex - count, tabs.length));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 |
a ** b |
a // b |
Math.floor(a / b) |
a %% b |
(a % b + b) % b |