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.
a << b
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.
例如，
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
.
9 << 3; // 72 // 9 * (2 ** 3) = 9 * (8) = 72
| 规范 |
|---|
|
ECMAScript (ECMA-262)
The definition of 'Bitwise Shift Operators' in that specification. |
| Desktop | Mobile | Server | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Bitwise left shift (
a << b
)
|
Chrome 1 | Edge 12 | Firefox 1 | IE 3 | Opera 3 | Safari 1 | WebView Android 1 | Chrome Android 18 | Firefox Android 4 | Opera Android 10.1 | Safari iOS 1 | Samsung Internet Android 1.0 | nodejs 0.1.100 |
完整支持