如何将两个if语句合并为一个？

Question

What is the simplest way to combine the following two if-statements into one if-statement?

if(n===1) return 0;
if(n===2) return 1;​

Answer 1

1) If you want to return for all numbers

You could simply say

return n-1;

2): If you want just for these two values

if (n === 1 || n === 2) return n-1;

Or something like bellow

[1,2].indexOf(n) //but this could be a tricky way.

Answer 2

if (n === 1 || n === 2) return n-1;