Bitwise shift right (>>) (Operator/bitwise)

Bitwise shift right one operand according to another.

Availability:

ECMAScript edition - 2
JavaScript - 1.0
JScript - 1.0
Internet Explorer - 3.02
Netscape - 2.0
Netscape Enterprise Server - 2.0
Opera - 3.0
Property/method value type:Number primitive
JavaScript syntax:-anOperand1 >> anOperand2
Argument list:anOperand1A value to be shifted
anOperand2A distance to shift the left operand

This is sometimes called shift right with sign extension.

The bitwise shift right operator converts its left operand to a 32 bit integer and moves it rightwards by the number of bits indicated by the right operand.

As the value is shifted rightwards, bits that roll out of the right end of the register are discarded. The left-hand end of the register containing the sign bit is duplicated to sign-fill the value as it shifts. Shifting rightwards by 32 bits will fill the buffer with all zero or all one bits according to the value of the sign bit at the outset.

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 rights by dividing values using powers of 2. Dividing a value by 2 shifts rightwards by one bit position.

Example code:

   <HTML>
   <HEAD></HEAD>
   <BODY>
   <SCRIPT>
   myValue1 = 0x00FF00;
   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>

See also:Associativity, Bit-field, Bitwise shift left (<<), Bitwise shift left then assign (<<=), Bitwise shift operator, Bitwise shift right and assign (>>=), Bitwise unsigned shift right (>>>), Bitwise unsigned shift right and assign (>>>=), Operator Precedence, Shift operator

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Cross-references:

ECMA 262 edition 2 - section - 11.7.2

ECMA 262 edition 3 - section - 11.7.2