javascript "for (;;);" structure [duplicate]

Question

Possible Duplicate:
Empty “for” loop in Facebook ajax
what does AJAX call response like for (;;); { json data } mean?

While analyzing some facebook ajax requests body i noticed that every code starts with for (;;);, folloed by an json object

something like

for (;;); {"a":1,"b":"\u003cdiv"}

I googled after this structure but found nothing.

What could be the reason for this "for" structure at the beginning of every ajax response?

Answer 1

A for like this (note that there isn't the ';' after the bracket):

for (;;)

means an infinite loop where the statements executed are those between the brackets.

Instead, a for like this:

for (;;);

means an infinite loop with no statement.