Add “http://” or “https://” to a URL that contain only the relative url starting by "www" - http

Question

Could someone help me to fix this little code to add the protocol “http://” or “https://” to a URL that contain only the relative url starting by "www"
<script>
function formatUrl(url)
{
var httpString = "http://";
var httpsString = "https://";
if (url.substr(0, httpString.length).toLowerCase() !== httpString && url.substr(0, httpsString.length).toLowerCase() !== httpsString)
url = httpString + url;
return url;
}
</script>
<form id=url type=get action='answers.asp' >
<input type=text name=URL size=10 value="" ><br><br>
<input type=submit name=url2 **onclick="formatUrl()"** value="Enter Url">
</form>
Input value = www.elmundo.es or any other relative url starting by www
thank you in advance

Answer 1

Actually this is a pretty simple task:
function formatURL(url)
{
if(url.substr(0,3) === "www")
{
return "https://"+url;
}
return url;
}
You may add some additional fail-safe checks (if the url is smaller than 3) - but you usually can check if the url starts with www, if so, you simply add the desired protocol to it (if I understood your question properly).
Ah, I guess now I got what you were asking for.
<script>
function formatURL()
{
var url = document.getElementsByName("URL")[0];
var formattedURL = document.getElementsByName("formattedURL")[0];
url = url.value;
if(url.substr(0,3) === "www")
{
formattedURL.value = "https://"+url;
return;
}
formattedURL.value = url;
}
</script>
<form id=url type=get action='answers.asp'>
<input type="text" name="URL" size=10 value="" onchange="formatURL()"><br><br>
<input type="hidden" name="formattedURL">
<input type="submit" value="Enter Url">
</form>
This will set the URL formatted into the hidden field formattedURL - however, this is only if you really want to do this in Javascript completely. I would do this on the server side, personally.