Below are some examples of doing form validation with Javascript. To be safe your final validation should be done server side. This is because Javascript code is executed client side. As we know we should never trust code the client can modify that we can not verify. You can use Javascript and serverside validation to help keep errors to a minimum and to check for any funny business someone is trying to put in the form fields (sql injeciton). Remember to escape all of those special characters in form fields.
Put all of the code examples from the links below between these script tags.
<script language="JavaScript"> <!-- //--> </script>
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;
}
}
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