Give it some thought. Have you figured it out yet?
Here is the explanation given at StackOverflow
The basic elements are as follows:
This is true, which can be coerced in to 1.
a >> b
The right-shift operator. In this case, it’s only used at the beginning of the expression as 0 >> 1 which evaluates to 0.
Bitwise XOR. Both usages above have either a or b are 0, and so the result is the non-zero operand.
[a] + [b]
String addition of a and b, evaluates to “ab”; if both a and b are numeric (e.g. + the result can be coerced into a numeric.
[a] * [b]
Multiplication can be performed on single element arrays, apparently. So this is equivalent to a*b.
a << b
The left-shift operator; for positive integers this effectively multiplies by 2 to the power of b. In the expression above, this is used with b = 0, so the result is a.
If you apply the correct order of operations, you get out  *  which evaluates to 42.