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What is Javascript Golfing?
Well, Javascript golfing is the process of writing the smallest amount of javascript code to do something awesome. It tests your ability to reduce, reuse, and recycle for the purpose of achieving the tiniest footprint possible. Also, it's fun!
Note: All of these games and more can be found here: Games.Zolmeister.com
First attempt, Snake:
My first attempt at golfing was inspired by MXSnake (back when I didn't even know it was called golfing). Here is my version: tinySnake (686 bytes). Kind of large, not too pretty and nothing really special, except my key events which I think are quite unique.
onkeydown=function(a){
q=a.which-38;
q%2?n=0:n=q-1;
q%2?e=q:e=0
}
I realized that the key presses should be directly tied to the movement variables of the snake, so I used the keyCode itself to set the movement (I think it could be done even more elegantly, but it's a start).
Second attempt, Pong:
My second attempt at golfing was inspired by an article on hacker-news I read about, where someone made tron in 219 bytes(!). Instead of trying to best them though, I made Pong (451 bytes) instead. (Screen is blank until you hit a key, W and A for p1 movement and UP and DOWN for p2 movement) Sadly I don't have the original non-compressed code, but my technique for compression mimicked the tron game.
Third Attempt, Two Towers:After feeling good about my pong implementation, I decided I wanted to make something new and original. I settled on a game where the player spawns objects to attack an enemy base. Another constraint I wanted to have was to keep it below 1KB (it's 1008 bytes currently), so that it could be compared to the applications at http://js1k.com (definitely check this out, there are some truly amazing apps people created). This time I did not lose the original non-compressed source:
//chrome auto-generates accessors for objects with ids
<body><canvas id=c width=700></canvas>Buy:
<script>
C=c.getContext('2d')
money=time=level=1//multiple assignments in one statement reduces the use of semicolons
upgrade=.99
R=Math.random;//assign common functions to variables
enemies=[{size:50, x:650, speed:-1/1e99}]//use e for large values (1e3=1000) - saved 1 byte
friendlies=[{size:50, x:70, speed:0}]//use unique variable names for easy hand-minification
C.fillRect(0,0,c.width,c.height);
part1="<button onclick='";
part2="</button>"
doc=document
for(i=3;i<10;i++)
doc.write(part1+"buy("+i+")'>$"+i*10+part2);
//using ~~ instead of parseInt helps a lot
doc.write(" Upgrade: "+part1+"upgradeValue=~~(200/upgrade-200)*10+100;money-upgradeValue<0?i:(upgrade-=.05,money-=upgradeValue);this.innerHTML=upgradeValue'>"+upgrade*100+part2);
//keep functions to a minimum (the word function is expensive)
//the function below gets removed and the whole thing inserted in an onclick event
function buy(n){
n=n/upgrade*10
money-=n*upgrade;
money<0?money+=n:friendlies.push({size:~~(Math.pow(n,2)/250)+5,x:100,speed:60/n});
}
function animation(){
if(R()<.03)//AI code (random is your friend)
enemies.push({size:~~(R()*level)+7, x:650, speed:-(level-R())})
C.clearRect(0,0,700,300);
C.fillText("$"+~~money,9,9)
//concat both friendlies and enemies for updating the objects (drawing and moving)
g=[].concat(enemies,friendlies)
for (i in enemies){
for (j in friendlies){
//during minification, && and || can usually be replaced by & and | respectively
if(friendlies[j].x+friendlies[j].size>=enemies[i].x-enemies[i].size && enemies[i].size>0 && friendlies[j].size>0){
--friendlies[j].size<0?friendlies[j].size++:i;
enemies[i].size==1?money+=enemies[i].size:i;
--enemies[i].size<0?enemies[i].size++:i;
enemies[i].x-=enemies[i].speed;
friendlies[j].x-=friendlies[j].speed;
}
}}
for (i in g){
g[i].x+=g[i].speed
//I used negative speed values to differenciate between enemies and friendlies
C.fillStyle=g[i].speed<0?'#F10':'#10F';
C.save()
time+=.01
C.translate(g[i].x,150-g[i].size)
C.rotate(time*(g[i].speed<0?-1:1))
C.font=g[i].size+'pt txt';
//thanks http://js1k.com/2010-first/demo/750 for the inspiration to use unicode
C.fillText(String.fromCharCode(1161),g[i].size/2,g[i].size/2)
C.restore()
}
//inline if statements are better if doing one action
//friendlies[0].size==0?history.go():i;
//function are special
friendlies[0].size==0&&history.go();
//regular ifs are more eficient for more than 1 call
if(enemies[0].size==0)friendlies=[friendlies[0]],enemies[0].size=50,level++,money+=500;
money+=.25;
time+=.1
}
//put the function inside of quotes in the interval call later to save space
setInterval(animation,50)
</script>
Finally, here are some tips for golfing:
Look at other peoples code. They come up with interesting tricks like this one (to remap the canvas calls to have shorter names):
for($ in C=c.getContext('2d'))C[$[0]+$[6]]=C[$]; Check out this tutorial on stackexchange.
Use a tool like jscrush after you hand-minify your code (and check that closure compiler won't help).
Good Luck!
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