JavaScript Programmer’s Reference Cross-references: ECMA 262 edition 2 (Michigan web site)
JavaScript Programmer’s Reference Cross-references: ECMA 262 edition 2 section 11.7.3 ECMA 262 edition 3 section 11.7.3 Bitwise unsigned shift right and assign (>>>=) (Operator/assignment) Destructively bitwise rightwards shift the first of two operands. 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 anOperand1 A value to be shifted and assigned to Argument list: anOperand2 A distance to shift the left operand Bitwise unsigned shift rightwards the left operand by the number of bits in the right operand and assign the result to the left operand. This is functionally equivalent to the expression: anOperand1 = anOperand1 >>> anOperand2; The bitwise unsigned 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. The sign bit is not propagated. 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 zero-filled as the contents are shifted. Shifting rightwards by 32 bits will fill the left operand 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. Although this is classified as an assignment operator it is really a compound of an assignment and a bitwise operator.