Bitwise AND (&) - JavaScript 编辑

The bitwise AND operator (&) returns a 1 in each bit position for which the corresponding bits of both operands are 1s.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Syntax

a & b

Description

The operands are converted to 32-bit integers and expressed by a series of bits (zeroes and ones). Numbers with more than 32 bits get their most significant bits discarded. For example, the following integer with more than 32 bits will be converted to a 32 bit integer:

Before: 11100110111110100000000000000110000000000001
After:              10100000000000000110000000000001

Each bit in the first operand is paired with the corresponding bit in the second operand: first bit to first bit, second bit to second bit, and so on.

The operator is applied to each pair of bits, and the result is constructed bitwise.

The truth table for the AND operation is:

a	b	a AND b
0	0	0
0	1	0
1	0	0
1	1	1

.    9 (base 10) = 00000000000000000000000000001001 (base 2)
    14 (base 10) = 00000000000000000000000000001110 (base 2)
                   --------------------------------
14 & 9 (base 10) = 00000000000000000000000000001000 (base 2) = 8 (base 10)

Bitwise ANDing any number x with 0 yields 0.

Examples

Using bitwise AND

// 5: 00000000000000000000000000000101
// 2: 00000000000000000000000000000010
5 & 2; // 0

Specifications

Specification
ECMAScript (ECMA-262) The definition of 'Bitwise AND expression' in that specification.

Browser compatibility

BCD tables only load in the browser

See also

• Bitwise operators in the JS guide
• Bitwise AND assignment operator