why ? 58

Question

What is the output of this code?
function zz(x,z,a,b) {
x = [9, 64, 20];
z = 50;
a = x[0] + 1;
b = x[2] - 2 ;
return z - a + b;
}
document.write(zz()); answer 58

Answer 1

z = 50
a = x[0] + 1 = 9 + 1 = 10
b = x[2] - 2 = 20 - 2 = 18

answer = z - a + b = 50 - 10 + 18 = 58

Answer 2

z is equal to 50
a is equal to x[0]+1. x[0] is 9, so a = 10
b is equal to x[2]-2. x[2] is 20, so b=18.
z-a+b is equivalent to 50-10+18, which equals 58.
Therefore, function zz() returns 58.