getUrlProtocol.js

surl = 'sdf:/900'; 
url = surl.toLowerCase();
var arr = url.split("://"); 
var protocol = arr[0];

console.log('protocol - '+protocol);

if(protocol === 'https')
{
  console.log('Its HTTPS');
}
else if(protocol === 'http')
{
  console.log('Its HTTP :(');
} 
else if( protocol === url)
{
  if(url.match(/^[a-zA-Z0-9]{1}/)){
    console.log('URL - '+'https://'+url);
  }else{
    console.log('Invalid');
  }
} 
else
{
  console.log('Invalid');
}