Comparing two JavaScript statements - are they equivalent?

Question

Are these two statements equivalent?

var var1 = var2 ? var2 : 0;

var var1 = var2 || 0;

Seems like yes, however I'm not sure.

var2 is (probably) defined above.

Answer 1

No, they're not:

> var i=0;
> with({ get var2() { return ++i; } }) {
>    var var1 = var2 || 0;
> }
> var1
1
> var i=0;
> with({ get var2() { return ++i; } }) {
>     var var1 = var2 ? var2 : 0;
> }
> var1
2

As you can see, the second one evaluates var2 twice. However, this is the only difference, and one that hardly matters for "normal" variables.