Javascript Form Validation

Put all of the code examples from the links below between these script tags.

E-Mail format checking script.

 if (document.formname.fieldname.value.length >0) {
	 i=document.formname.fieldname.value.indexOf("@")
	 j=document.formname.fieldname.value.indexOf(".",i)
	 k=document.formname.fieldname.value.indexOf(",")
	 kk=document.formname.fieldname.value.indexOf(" ")
	 jj=document.formname.fieldname.value.lastIndexOf(".")+1
	 len=document.formname.fieldname.value.length

 	if ((i>0) && (j>(1+1)) && (k==-1) && (kk==-1) && (len-jj >=2) && (len-jj<=3)) {
 	}
 	else {
 		alert("Please enter an exact email address.\n" +
		document.formname.fieldname.value + " is invalid.");
		return false;
 	}

 }

Check if field has special characters.

  var iChars = "!@#$%^&*()+=-[]\\\';,./{}|\":<>?";

  for (var i = 0; i < document.formname.fieldname.value.length; i++) {
  	if (iChars.indexOf(document.formname.fieldname.value.charAt(i)) != -1) {
  	alert ("Your username has special characters. \nThese are not allowed.\n Please remove them and try again.");
  	return false;
  	}
  }

Check if certian radio buttons have not been selected.

    if (!document.formname.fieldname[0].checked &&
    	!document.formname.fieldname[1].checked &&
    	!document.formname.fieldname[2].checked &&
    	!document.formname.fieldname[3].checked) {
    	alert("Please choose a group designation.\n");
    	return false;
    }

Check if textbox has any characters in it.

     if (document.formname.fieldname.value.length == 0) {
          alert("Please fill out your name.\n");
	  return false;
     }

Check if multiple checkboxes have not been selected.Replace false with true to see if all are selected.

     if (document.formname.fieldname.checked == false &&
         document.formname.fieldname.checked == false &&
	 document.formname.fieldname.checked == false) {
	  
	 alert("Please select at least one checkbox.\n");
	 return false;
     }

Check drop down has been selected. Set drop down's value to Not_Selected for this to work.

     if (document.formname.fieldname.value == 'Not_Selected') {
          alert("Please provide us with a selection.\n");
          return false;
     }

Scan values in a field and if they are all letters then alert. The second block of code does the same but for numbers

//alert on finding all letters
    var noalpha = /^[a-zA-Z]*$/;
if (noalpha.test(document.formname.fieldname.value)) {
     alert("Please enter at least one number in the \"username\" field.");
     return false;
}

//alert on finding all numbers
var nonums = /^[0-9]*$/;
if (nonums.test(document.formname.fieldname.value)) {
     alert("Please enter at least one letter in the \"username\" field.");
     return false;
}

Remove special characters from a string.

function clearText() {
     document.formname.fieldname.value=filterNum(document.formname.fieldname.value)

     function filterNum(str) {
          re = /\$|,|@|#|~|`|\%|\*|\^|\&|\(|\)|\+|\=|\[|\-|\_|\]|\[|\}|\{|\;|\:|\'|\"|\<|\>|\?|\||\\|\!|\$|\./g;
          // remove special characters like "$" and "," etc...
          return str.replace(re, "");
     }
}

Detect special characters in text box. Or any character you subsitute for the special characters.

     var iChars = "!@#$%^&*()+=-[]\\\';,./{}|\":<>?";
        for (var i = 0; i < document.formname.fieldname.value.length; i++) {
                if (iChars.indexOf(document.formname.fieldname.value.charAt(i)) != -1) {
                alert ("The box has special characters. \nThese are not allowed.\n");
                return false;
        }
                }

form validation javascript