Sierpinski triangle - 140byt.es

annotated.js

function(){
  /* Rules:                      // make sure
  (1) anonymous function         // to annotate
  (2) optionally self-executing  // your code
  (3) <140 bytes                 // so everyone
  (4) no global vars             // can learn
  (5) MIT license                // from it!
  (6) good luck!
*/}

index.js

function(){/*Rules: (1) anonymous function (2) optionally self-executing (3) <140 bytes (4) no global vars (5) MIT license (6) good luck!*/}

package.json

{
  "name": "sample",
  "keywords": [ "sample", "original" ]
}

9 bytes smaller:
function(c,s,i,a,b,r){for(a=b=0;i--;r=Math.random())c.fillRect(a=(r>2/3&&s)+a>>1,b=(r<1/3&&s)+b>>1,1,1)}

@williammalo
Results will be different though, because r will be undefined the first time the loop runs. This should work and be a byte smaller too:

``` function(c,s,i,a,b){for(a=b=0;i--;)r=Math.random(),c.fillRect(a=(r>2/3&&s)+a>>1,b=(r<1/3&&s)+b>>1,1,1)}``

@xpansive
"r" will leak to the global scope.

Also, 20 bytes smaller than the original:
function(c,s,i,a,b,r){for(;i--;r=Math.random()_3)c.fillRect(a=(r>2)_s+a>>1,b=(r<1)*s+b>>1,1,1)}

Whoops, totally missed that.

@williammalo
Thanks a lot for your improvements; I adjusted the code according to your last variant. Values "a" and "b" are now rounded each iteration (difference from my original version), but I suppose that is not a problem :-)

@ondra Thanks! :)
1 byte smaller!:
function(c,s,i,a,b,r){for(;i--;r=Math.random()_3)c.fillRect(a=(r>2)_s+a>>1,b=!~~r*s+b>>1,1,1)}