isOn2

isOn2 is a JavaScript function designed to determine if a given number is an "on-two" number. An on-two number is defined as a positive integer where the number of set bits (bits with a value of 1) in its binary representation is equal to two.

The function checks for two conditions. First, it verifies that the input `n` is indeed a number and is a positive integer. If `n` is not a number, is negative, or is not an integer, the function will return false, indicating that it cannot be an on-two number.

If the input passes these initial checks, the function proceeds to count the set bits in the binary representation of `n`. This is typically achieved through bitwise operations. A common method involves repeatedly checking the least significant bit and right-shifting the number until it becomes zero. For example, `n & 1` checks if the last bit is 1, and `n >>>= 1` performs an unsigned right shift.

Once the count of set bits is obtained, the function compares this count to the value 2. If the number of set bits is exactly two, the function returns true, signifying that the input number is an on-two number. Otherwise, it returns false. Examples of on-two numbers include 3 (binary 11), 5 (binary 101), and 6 (binary 110).