const num = 42; // 00101010
const result: number = num.toString(2)
.split('')
.reduce((parity: number, bit: any) => parity ^ bit, 0)
console.log("0 = even number of bits set");
console.log("1 = odd number of bits set");
console.log("result: " + result);
/*
run:
"0 = even number of bits set"
"1 = odd number of bits set"
"result: 1"
*/