 | JavaScript | |||
|---|---|---|---|---|
| Prev | Home | Up | Next |
| Availability: |
| ||||||||
| Property/method value type: | Number primitive | ||||||||
| JavaScript syntax: | - | anOperand1 << anOperand2 | |||||||
| Argument list: | anOperand1 | A value to be shifted | |||||||
| anOperand2 | A distance to shift anOperand1 | ||||||||
The bitwise shift left operator converts its left operand to a 32 bit integer and moves it leftwards by the number of bits indicated by the right operand.
As the value is shifted leftwards, bits that roll out of the left end of the register are discarded. The right-hand end of the register is filled with zero bits. Shifting leftwards by 32 bits will fill the register with all zero bits.
Because the value is converted to an integer, any fractional part is discarded as the shift begins.
The right-hand operand is converted to a 5 bit value with a bitwise mask to limit the distance of the shift to 32 bits. This can cause unexpected results if the right-hand side is derived from an expression that may yield a value larger than 32.
The associativity is left to right.
Refer to the Operator Precedence topic for details of execution order.
You can accomplish bitwise shift lefts by multiplying values using powers of 2. Multiplying a value by 2 shifts leftwards by one bit position.
<HTML>
<HEAD></HEAD>
<BODY>
<SCRIPT>
myValue1 = 0x00FF;
myValue2 = myValue1 << 4;
document.write("Val 1 : " + binary32(myValue1) + "<BR>");
document.write("Result : " + binary32(myValue2) + "<BR>");
// Binary convertor (ignore sign bit on MSIE)
function binary32(aValue)
{
myArray = new Array(32);
for(myEnum=0; myEnum<32; myEnum++)
{
if(aValue & Math.pow(2, myEnum))
{
myArray[31-myEnum] = "1";
}
else
{
myArray[31-myEnum] = "0";
}
}
return myArray.join("");
}
</SCRIPT>
</BODY>
</HTML>| Prev | Home | Next |
| Bitwise OR then assign (|=) | Up | Bitwise shift left then assign (<<=) |
JavaScript Programmer's Reference, Cliff Wootton Wrox Press (www.wrox.com) Join the Wrox JavaScript forum at p2p.wrox.com Please report problems to support@wrox.com © 2001 Wrox Press. All Rights Reserved. Terms and conditions. | ||
