/**
 * Validates that input's value is correct email address
 */
function validateEmail(elem) {
    var str = "";
    if (elem.value) {
        str = new String(elem.value);
    } else {
        str = new String(elem);
    }

    if (window.RegExp) {
        var reg1str = "(@.*@)|(\\.\\.)|(@\\.)|(\\.@)|(^\\.)";
        var reg2str = "^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,4}|[0-9]{1,4})(\\]?)$";
        var reg3str = "\"([^\"]+)\"\\s+<{1}([A-z]{1}[A-z0-9\\x2d\\.]*[A-z0-9]{1}@[A-z0-9\\x2d\\.]*[A-z-9]{1}\\.[A-z]{2,5})>{1}";
        var reg1 = new RegExp(reg1str);
        var reg2 = new RegExp(reg2str);
        var reg3 = new RegExp(reg3str);
        if (!reg1.test(str) && (reg2.test(str) || reg3.test(str))) return true;
        return false;
    } else {
        if (str.indexOf("@") >= 0) return true;
        return false;
    }
}
/**
 * Returns value of selected option in listbox
 * If there is no options selected - returns null.
 * If multiple options selected - returns first.
 */

function selected(sel){
  if(!sel.options){
     return null;
  }
  for(var i = 0; i< sel.options.length; i++){
     if(sel.options[i].selected){
        return sel.options[i].value;
     }
  }

  return null;
}

/**
 * Returns value of checked radiobutton in radiobuttons group
 * If there is no radiobuttons checked - returns null.
 */

function selectedRadio(sel){
  if(!sel){
     return null;
  }
  if(!sel.length){
     if(!sel.checked){
        return null;
     }
     return true;
  }
  for(var i = 0; i< sel.length; i++){
     if(sel[i].checked){
        return sel[i].value;
     }
  }
  return null;
}

/**
 * Returns true if one of options in radiogroup is checked;
 */
function isChecked(sel){
  return selectedRadio(sel) != null;
}
String.prototype.trim = function() {
    return this.replace(/(^\s*)|(\s*$)/g, "");
}

/**
 * returns string with all leading and trailing characters 
 * eliminated.
 */
function trim(str){
  var s = new String(str);
  //trailing spaces
  while (s.length>0 && isSpaceCharacter(""+s.charAt(s.length-1))){
    s = s.substring(0,s.length-1);
  }
  //leading spaces
  while (s.length>0 && isSpaceCharacter(""+s.charAt(0))){
    s = s.substring(1);
  }
  return s
}

var spaces = " \t\r\n"+String.fromCharCode(160);

function isSpaceCharacter(ch){
  return spaces.indexOf(ch) >-1;
}
function isEmpty(elem){
  return trim(elem.value).length==0;
}

function validateForm(){

  if(isEmpty(f.name)){
    alert("Please enter name");
    f.name.focus();
    return false;
  }
  if(isEmpty(f.email) || !validateEmail(f.email)){
    alert("Please enter valid email address");
    f.email.focus();
    return false;
  }
  if(isEmpty(f.phone)){
    alert("Please enter phone");
    f.phone.focus();
    return false;
  }

  if(isEmpty(f.contactmessage)){
    alert("Please enter sending message");
    f.contactmessage.focus();
    return false;
  }

  f.submit();
}