<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>Спойлеры</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js"></script>
<style>
*{
margin:0;
padding:0;
outline: 0;
}
input:hover {
outline: none;
}
input{
margin-left: 50px;
margin-top: 10px;
}
input[type="text"]:first-child{
margin-bottom: 10px;
}
input[type="button"] {
display: block;
width: 150px;
height:30px;
margin-bottom: 10px;
}
</style>
</head>
<body>
<input name="telnumber" type="text">
<input name="telbutton" type="button" value='Нажми меня'>
<input name="telnumberresult" type="text">
<script>
var button = document.getElementsByName("telbutton")[0];
button.onclick = function(){
var telNumber = document.getElementsByName("telnumber")[0].value;
var telNumberResultElem = document.getElementsByName("telnumberresult")[0];
var number=telNumber.replace(/\D/gm,'');
if (number.length>11 || number.length<10)
alert('Вы неправильно ввели моб. телефон');
else if((number[0]!=='8' && number[0]!=='7')&&(number.length=='11'))
alert('Вы неправильно ввели моб. телефон');
else telNumberResultElem.value = number;
}
</script>
</body>
</html>