<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <script type="text/javascript"> function IPv4Validate(myfield, e) { if (!e) var e = window.event if (e.keyCode) code = e.keyCode; else if (e.which) code = e.which; var character = String.fromCharCode(code); // if they pressed esc... remove focus from field... if (code==27) { this.blur(); return false; } if ( e.ctrlKey || code == 8 || code == 9 || code == 36 || code == 37 || code == 38 || (code == 39 && (code != 39 || character != "'") ) || code == 40) return false; var integerOnly = /[0-9\.]/g; if ( ! character.match(integerOnly)) return false; var str = myfield.value + character; var pattern = /\d{1,3}\.?/g; var result = str.match(pattern); if ( ! result ) return false; if ( result.length > 4 ) return false; for (var i = 0; i < result.length; i++ ) { var pp = /\d{1,3}\./g; if ( (i != result.length - 1) && ! result[i].match(pp) ) return false; else if ( i == 3 ) { pp = /\./g; if ( result[3].match(pp) ) return false; } var str = result[i]; str.replace(".", ""); if ( parseInt(str) > 255 ) return false; } return true; } </script> </head> <body> <p><label for="inputIPv4">IPv4 address only</label> <input type="text" id="inputIPv4" onkeypress="return IPv4Validate(this, event);" /></p> </body> </html>