What a strange syntax?

Question

I\'ve found unknown for me code construction on JQuery site. After some formatting it looks like:

function (a,c) {
    c==null && (c=a,a=null);
            


        

Answer 1

It's a trick that uses boolean short-circuit evaluation to only do the second half if the first evaluates to true. Perl has this commonly:

 or die

where if the first statement failed, the program ends.

Read it as

if (c == null) { c = a; a = null; }