Question

I was under the impression that

setInterval("/*some code*/", time)

was equivalent to

setInterval(function() {
   /*some code*/
}, time)

Apparently not! Please compare the following (full HTML):

<pre id=p><script>n=setInterval("for(n+=7,i=k,P='p.\\n';i-=1/k;P+=P[i%2?(i%2*j-j+n/k^j)&1:2])j=k/i;p.innerHTML=P",k=64)</script>

and

<pre id=p><script>n=setInterval(function() { for(n+=7,i=k,P='p.\\n';i-=1/k;P+=P[i%2?(i%2*j-j+n/k^j)&1:2])j=k/i;p.innerHTML=P },k=64)</script>

The two animations (the first being taken from here) are different.

Why are the two constructs not equivalent?

Answer: There are at least three differences

1. Variable scope
2. Performance
3. String character escapes

Answer 1

Those two forms of setInterval are essentially equivalent — but your code isn’t. In the second example you’re double-escaping your newline as \\n, instead of just \n. Try this:

<pre id=p><script>n=setInterval(function() { for(n+=7,i=k,P='p.\n';i-=1/k;P+=P[i%2?(i%2*j-j+n/k^j)&1:2])j=k/i;p.innerHTML=P },k=64)</script>

And that should be just like what you want.

The function() form of setInterval is better in a lot of ways — it’s more readable, and as you ran into here, you don’t have to deal with trying to escape strings inside of string.