Left shift (<<)

The left shift operator (<<) shifts the first operand the specified number of bits to the left. Excess bits shifted off to the left are discarded. Zero bits are shifted in from the right.

Syntax

a << b

Description

This operator shifts the first operand the specified number of bits to the left. Excess bits shifted off to the left are discarded. Zero bits are shifted in from the right.

For example, 9 << 2 yields 36:

.    9 (base 10): 00000000000000000000000000001001 (base 2)
                  --------------------------------
9 << 2 (base 10): 00000000000000000000000000100100 (base 2) = 36 (base 10)

Bitwise shifting any number x to the left by y bits yields x * 2 ** y.
So e.g.: 9 << 3 translates to: 9 * (2 ** 3) = 9 * (8) = 72.

Examples

Using left shift

9 << 3; // 72

// 9 * (2 ** 3) = 9 * (8) = 72

Specifications

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

Browser compatibility

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See also