console.log(protect_email("robin_singh@example.com"));
function protect_email(str)
{
    var temp = str.split('')
    var ar = [];
    var ch ='...';
    for(var i = 0 ; i< temp.length ; i++)
    {
       if(i>4 && i<12)
        {
            if(i==11)
            {
                ar[i]=ch;
                ar.push(temp[i]);
            }
         }
        else
        {
        ar.push(temp[i]);    
        }
    }
    return ar.join('')
}