Question

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What does this construct (x = x || y) mean?

I’ve seen this code here. And some similar code on other places that I can’t recall.

1. time = jQuery.fx ? jQuery.fx.speeds[time] || time : time;

2. type = type || "fx";

What does it mean?

I don’t understand a) at all but I *think* I understand b) like this:

If type is false then type will be equal to "fx" otherwise type will equal whatever it was before.

I’m not sure, but perhaps I’m wrong.

What is this syntax called? Conditional variable? 😛 I tried Googling for an answer but have no idea what to use in my query.

Answer 1

a)

time = jQuery.fx ? jQuery.fx.speeds[time] || time : time;

is synonym for

if (jQuery.fx) {
    if (jQuery.fx.speeds[time]) {
        time = jQuery.fx.speeds[time];
    }
}

which is almost the same as

b)

type = type || "fx";

is synonym for

if (!type) {
   type = "fx";
}

Simply it checks if type is not false, null, undefined. If yes, type is being filled with fx