pvdz.ee - 11.7.3 Unsigned right shift operator >>>

Shift bits to the left. Like >>>, this operator ignores the sign and fills left bits with zeros.

ShiftExpression : ShiftExpression >>> AdditiveExpression

Code: (Meta Ecma)

function evaluate(ShiftExpression >>> AdditiveExpression) {
  var lref = evaluate(ShiftExpression);
  var lval = GetValue(lref);
  var rref = evaluate(AdditiveExpression);
  var rval = GetValue(rref);
  var lnum = ToUint32(lval);
  var rnum = ToUint32(rval);
  var shiftCount = rnum & 0x1F;
  return lnum >>> shiftCount; // result is an unsigned (!) 32bit int
}

Note that the left bits are always filled with zeros, unlike >> which uses the sign to fill. See 11.7 for more examples.

This operator can mimic the ToUint32() operation by n>>>0.