JS Bitwise

JavaScript Bitwise Operators

Examples

JavaScript Uses 32 bits Bitwise Operands

JavaScript stores numbers as 64 bits floating point numbers, but all bitwise operations are performed on 32 bits binary numbers.

Before a bitwise operation is performed, JavaScript converts numbers to 32 bits signed integers.

After the bitwise operation is performed, the result is converted back to 64 bits JavaScript numbers.

Note: The examples above uses 4 bits unsigned binary numbers. Because of this ~ 5 returns 10. Since JavaScript uses 32 bits signed integers, it will not return 10. It will return -6. 00000000000000000000000000000101 (5) 11111111111111111111111111111010 (~5 = -6) A signed integer uses the leftmost bit as the minus sign.

JavaScript Bitwise AND

When a bitwise AND is performed on a pair of bits, it returns 1 if both bits are 1.

JavaScript Bitwise OR

When a bitwise OR is performed on a pair of bits, it returns 1 if one of the bits is 1:

JavaScript Bitwise XOR

When a bitwise XOR is performed on a pair of bits, it returns 1 if the bits are different:

JavaScript Bitwise AND (&)

Bitwise AND returns 1 only if both bits are 1:

Example

let x = 5 & 1;

JavaScript Bitwise OR (|)

Bitwise OR returns 1 if one of the bits is 1:

Example

let x = 5 | 1;

JavaScript Bitwise XOR (^)

Bitwise XOR returns 1 if the bits are different:

Example

let x = 5 ^ 1;

JavaScript Bitwise NOT (~)

Example

let x = ~5;

JavaScript (Zero Fill) Bitwise Left Shift (<<)

This is a zero fill left shift. One or more zero bits are pushed in from the right, and the leftmost bits fall off:

Example

let x = 5 << 1;

JavaScript (Sign Preserving) Bitwise Right Shift (>>)

This is a sign preserving right shift. Copies of the leftmost bit are pushed in from the left, and the rightmost bits fall off:

Example

let x = -5 >> 1;

JavaScript (Zero Fill) Right Shift (>>>)

This is a zero fill right shift. One or more zero bits are pushed in from the left, and the rightmost bits fall off:

Example

let x = 5 >>> 1;

Shift Assignment Operators

The <<= Operator

The Left Shift Assignment Operator left shifts a variable.

Left Shift Assignment Example

let x = -100;

x <<= 5;

The >>= Operator

The Right Shift Assignment Operator right shifts a variable (signed).

Right Shift Assignment Example

let x = -100;

x >>= 5;

The >>>= Operator

The Unsigned Right Shift Assignment Operator right shifts a variable (unsigned).

Unsigned Right Shift Assignment Example

let x = -100;

x >>>= 5;

Bitwise Assignment Operators

The &= Operator

The Bitwise AND Assignment Operator does a bitwise AND operation on two operands and assigns the result to the the variable.

Bitwise AND Assignment Example

let x = 10;

x &= 5;

The |= Operator

The Bitwise OR Assignment Operator does a bitwise OR operation on two operands and assigns the result to the variable.

Bitwise OR Assignment Example

let x = 10;

x |= 5;

The ^= Operator

The Bitwise XOR Assignment Operator does a bitwise XOR operation on two operands and assigns the result to the variable.

Bitwise XOR Assignment Example

let x = 10;

x ^= 5;

Binary Numbers

Binary numbers with only one bit set are easy to understand:

Setting a few more bits reveals the binary pattern:

JavaScript binary numbers are stored in two's complement format.

This means that a negative number is the bitwise NOT of the number plus 1:

Note: Joke: There are only 10 types of people in the world: those who understand binary and those who don't.

Converting Decimal to Binary

Example

function dec2bin(dec){

  return (dec >>> 0).toString(2);

}

Converting Binary to Decimal

Example

function bin2dec(bin){

    return parseInt(bin, 2).toString(10);

}