Double semicolons syntax in javascript

Question

Can someone tell me what double semicolons (;;) in javascript means? I see them in fullcalendar.js.

Thanks.

Here\'s a snippet of the fullcalendar.js code (ta

Answer 1

Empty “for” loop

for(;;){...} is the same as saying while(1){...}

for(;;) jumps out to mean "infinite loop" more readily than while(1)

facebook's AJAX responses all start with an empty for loop.

Answer 2

The double semicolons ;; has nothing to do with a for loop in the case of fullcalendar.js (which is now on github).

There is no value to the parsing or execution of the code itself (it is basically innocuous); rather the author has used ;; merely as a sentinel to separate logical chunks of code. It was a weird and esoteric choice to do this, but as it turns out it is very helpful to use CTRL-F to search for ;; to jump from one section to another (for example, the class definitions appear to be separated in this way).

The author could have used comments, for example:

/* ;; */

or

/* CLASSDEF */

etc., but he didn't.

Also confirmed: the JavaScript minifiers I tested remove the ;; so definitely not critical to the code, and not helpful as a sentinel when searching minified code. (but neither are comments because they are stripped out).