Get Bit

We can use bitwise and operator to test if specific bit is 1 or 0.

function getBit(number, bitPosition) {
    return (number >> bitPosition) & 1;
}

const x = 0b10101010;

for (let i = 0; i < 8; i++) {
    const bit = getBit(x, i);
    console.log(bit);
}
// 0
// 1
// 0
// 1
// 0
// 1
// 0
// 1

Set Bit

We can use bitwise or operation to set specific position to 1 or 0.

function getBit(number, bitPosition) {
    return (number >> bitPosition) & 1;
}

function setBit(number, bitPosition, bitValue) {
    const clearMask = ~(1 << bitPosition);

    // make bitPosition 0
    number = number & clearMask;

    // set bitValue
    number = number | (bitValue << bitPosition);

    return number;
}

let x = 0;

x = setBit(x, 5, 1);
console.log(getBit(x, 5)) // 1

x = setBit(x, 5, 0);
console.log(getBit(x, 5)) // 0

isEven

Odd numbers have their last right bit to be set to 1.

function isEven(number) {
    return (number & 1) === 0;
}

console.log(isEven(5)) // false
console.log(isEven(6)) // true

Multiply By Two

Left shift equals to multiple by 2.

function multiplyByTwo(number) {
    return number << 1;
}

console.log(multiplyByTwo(2)) // 4

Divide By Two

Right shift equals to divide by 2.

function divideByTwo(number) {
    return number >> 1;
}

console.log(divideByTwo(2)) // 1