SIMD.js has been taken out of active development in TC39 and removed from Stage 3. It is not being pursued by web browsers for implementation anymore. SIMD operations exposed to the web are under active development within WebAssembly, with operations based on the SIMD.js operations.

The static SIMD.%type%.shiftLeftByScalar() method returns a new instance with the lane values shifted left by a given bit count (a << bits).


SIMD.Int8x16.shiftLeftByScalar(a, bits)
SIMD.Int16x8.shiftLeftByScalar(a, bits)
SIMD.Int32x4.shiftLeftByScalar(a, bits)

SIMD.Uint8x16.shiftLeftByScalar(a, bits)
SIMD.Uint16x8.shiftLeftByScalar(a, bits)
SIMD.Uint32x4.shiftLeftByScalar(a, bits)


An instance of a SIMD type.
Bit count to shift by.

Return value

A new corresponding SIMD data type with the lane values shifted left by a given bit count (a << bits).


The bitwise left shift operation shifts 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, a bitwise left shift of 5 << 1 results in 1010 which is 10 in decimal.

5  0101
10 1010


Bitwise left shift of an Int32x4

var a = SIMD.Int32x4(1, 2, 4, 8);
SIMD.Int32x4.shiftLeftByScalar(a, 1);
// Int32x4[2, 4, 8, 16]


Specification Status Comment
The definition of 'SIMDConstructor.shiftLeftByScalar' in that specification.
Obsolete Initial definition.

Browser compatibility

Experimental SIMD.js has been removed from browsers. It's still available in Firefox Nightly, but will be removed in favor of a SIMD implementation in WebAssembly. See also bug 1416723.

See also

Document Tags and Contributors

 Contributors to this page: fscholz
 Last updated by: fscholz,