&& operator in Javascript

Question

While looking through some code (javascript), I found this piece of code:

Answer 1

&& is an AND operator, just like most everywhere else. There is really nothing fancy about it.

Most languages, JavaScript included, will stop evaluating an AND operator if the first operand is false.

In this case, if window.Bootloader does not exist, it will be undef, which evaluates to false, so JavaScript will skip the second part.

If it is true, it continues and calls Bootloader.done(...).

Think of it as a shortcut for if(window.Bootloader) { Bootloader.done(...) }