How do you set, clear and toggle a single bit in JavaScript?

Question

How to set, clear, toggle and check a bit in JavaScript?

Answer 1

To get a bit mask:

var mask = 1 << 5; // gets the 6th bit

To test if a bit is set:

if ((n & mask) != 0) {
  // bit is set
} else {
  // bit is not set
}

To set a bit:

n |= mask;

To clear a bit:

n &= ~mask;

To toggle a bit:

n ^= mask;

Refer to the Javascript bitwise operators.

Answer 2

I want to add some things (with thanks to @cletus)

function bit_test(num, bit){
    return ((num>>bit) % 2 != 0)
}

function bit_set(num, bit){
    return num | 1<<bit;
}

function bit_clear(num, bit){
    return num & ~(1<<bit);
}

function bit_toggle(num, bit){
    return bit_test(num, bit) ? bit_clear(num, bit) : bit_set(num, bit);
}

Answer 3

Get Bit

function getBit(number, bitPosition) {
  return (number & (1 << bitPosition)) === 0 ? 0 : 1;
}

Set Bit

function setBit(number, bitPosition) {
  return number | (1 << bitPosition);
}

Clear Bit

function clearBit(number, bitPosition) {
  const mask = ~(1 << bitPosition);
  return number & mask;
}

Update Bit

function updateBit(number, bitPosition, bitValue) {
  const bitValueNormalized = bitValue ? 1 : 0;
  const clearMask = ~(1 << bitPosition);
  return (number & clearMask) | (bitValueNormalized << bitPosition);
}

Examples has been taken from JavaScript Algorithms and Data Structures repository.

Answer 4

I built a BitSet class with the help of @cletus information:

function BitSet() {
    this.n = 0;
}

BitSet.prototype.set = function(p) {
    this.n |= (1 << p);
}

BitSet.prototype.test = function(p) {
    return (this.n & (1 << p)) !== 0;
}

BitSet.prototype.clear = function(p) {
    this.n &= ~(1 << p);
}

BitSet.prototype.toggle = function(p) {
    this.n ^= (1 << p);
}