Hack to convert javascript number to UInt32

Question

Edit: This question is out of date as the Polyfill example has been updated. I\'m leaving the question here just for reference. Read the correct answer for usef

Answer 1

The ECMAScript specification states that the value is converted to UInt32 in step 5 and 8 of http://www.ecma-international.org/ecma-262/5.1/#sec-11.7:

11.7.3 The Unsigned Right Shift Operator ( >>> )

Performs a zero-filling bitwise right shift operation on the left operand by the amount > specified by the right operand.

The production ShiftExpression : ShiftExpression >>> AdditiveExpression is evaluated as follows:

1. Let lref be the result of evaluating ShiftExpression.
2. Let lval be GetValue(lref).
3. Let rref be the result of evaluating AdditiveExpression.
4. Let rval be GetValue(rref).
5. Let lnum be ToUint32(lval).
6. Let rnum be ToUint32(rval).
7. Let shiftCount be the result of masking out all but the least significant 5 bits of rnum, that is, compute rnum & 0x1F.
8. Return the result of performing a zero-filling right shift of lnum by shiftCount bits. Vacated bits are filled with zero. The result is an unsigned 32-bit integer.