String manipulation is one of the most basic things you need to know.
<form id="reverse" action="javascript:doIT()"> <table> <th colspan="2">Reverse String</th> <tr> <td><input type="text" id="string" placeholder="enter a string" required /></td> </tr> <tr> <td class="button"><input type="submit" id="reverse" value="Reverse" /></td> </tr> <tr> <td><strong>LOG :</strong><br/><div id="log"></div></td> </tr> </table> </form> <script> function doIT(){ var string = document.getElementById("string"); var log = document.getElementById("log"); log.innerHTML += " " + string.value + " = " + reversal(string.value) + "<br/>"; string.value = reversal(string.value); } function reversal(s) { var r = s.split("").reverse().join(""); return r; } </script>DEMO | DOWNLOAD