<input type = 'text' name = 'URL'>

var url="test.com";
if (url.substring(0,7) != "http://")
url = "http://" + url;
alert(url);

var normalizeUrl = function (url) {
    if( !/^https?:///i.test(url) ) {
        url = 'http://' + url;
    }
    return url;
}