javascript:(function() {var input = prompt("Please enter a properly formatted string for the parser to look at:");if (!/^[\d?]+$/.test(input)) {/* This is a regular expression In javascript, they're represented by two forward slashes. This regex : ^ # Assert the beginning of the string. [ # This is a character class (match anything in between here) \d # Match any digit ? # Match question marks ] + # Repeat the previous class as much as possible. $ # Assert the end of the string.*/ alert("Erroneous syntax!"); return;}/* At this point, the input is verified and no further error checking is needed.*/var out = "", currentChar;for(var i = 0; i < input.length; ++i) { currentChar = input.charAt(i); if(/\d+/.test(currentChar)) { out += currentChar; } else { out += Math.round(Math.random() * 9); }}alert(out);})();