How to validate a text string using javascript?

Question

So I want to create a prompt that asks for a clients name. I want to make sure it is formatted in this way: "Last name, first name, middle initial" and no name longer than 20 characters. Here is what I have so far, but not sure where to go from here.

<script language="JavaScript">
//Get the name
var name = prompt("What is your Name?");

//validate
if(name)
//output
document.write ("That is your name! :)");

else
document.write ("Please use the format Last name, first name, middle initial");
 </script>

First, using document.write is usually not a good idea. Also, is the 20 character limit based on the full name or each of the parts? What happens if someone does not have a middle name or surname? — Qantas 94 Heavy
– Qantas 94 Heavy, Commented Dec 13, 2013 at 4:05
Client side validation is fine but make sure to have server side validation as well. Clients could disable javascript. — Harry
– Harry, Commented Dec 13, 2013 at 4:06
the prompt is just for testing. actually it is supposed to be a max of 20 characters per name — user3097967
– user3097967, Commented Dec 13, 2013 at 4:54

HardikS · Accepted Answer · 2013-12-13 05:04:02Z

4

Have a look at the below simple steps using regular expression :

// Get name
var name = prompt("What is your Name?");

// match name with regular expression
if (name.match("^[A-Za-z]{1,20}, [A-Za-z]{1,20}, [A-Za-z]{1,20}")) {
    document.write("That is your name! :)");
} else {
    document.write("Please use the format Last name, first name, middle initial");
}

Result :

Match :

abc, xyz, m ,
abcabcabc, xyzzyz, mr

Non Matchs :

, xyz, m ,
123, a, b,
iammorethantwentycharactersfirstname, middle, initial

edited Dec 13, 2013 at 5:04

answered Dec 13, 2013 at 4:58

HardikS

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1 Comment

jasonscript Over a year ago

The last regex part should be [A-Za-z]{1} because the OP is just looking for a middle name initial, but +1 for the explanation

RobG · Accepted Answer · 2013-12-13 04:30:16Z

0

To exactly fit your criteria:

var s = 'smith, john, j';
var isValid = /^\w+, \w+, \w$/.test(s) && s.replace(/[, ]/g,'').length < 21;

but that is very specific and assumes the 20 character limit applies to the total of the parts of the name and doesn't inlcude any spaces, commas, etc. BTW, the above will fail for hyphenated names so the regular expression might need to be:

/^[\w-]+, [\w-]+, \w$/;

to allow say 'Smith-Jones, Mary-Jo, A'.

answered Dec 13, 2013 at 4:30

RobG

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4 Comments

user3097967 Over a year ago

This seems to be what I am looking for, but how do I use that validation to pass a valid or invalid message to the output?

Qantas 94 Heavy Over a year ago

@user3097967: isValid is a boolean, use that for your if condition. And I'll ask again: is the 20 character limit based on the full name or each of the parts?

user3097967 Over a year ago

Hmm not sure I am getting it. Here is what I have (obviously wrong) <script language="JavaScript"> //Get the name var name = prompt("What is your Name?"); //validate var isValid = /^\w+, \w+, \w$/.test(s) && s.replace(/[, ]/g,'').length < 21; if(name isValid) { document.write ("Invalid name"); } else{ //output document.write ("Valid name"); } </script>

RobG Over a year ago

Just if (isValid) ....

iCezz · Accepted Answer · 2013-12-13 04:42:53Z

0

Your code should be like:

<script language="JavaScript">
    //Get the name
    var name = prompt("What is your Name?");

    //validate
    if(name && name.length <=20)
    {
        var i = name.split(',');
        if(i.length<3){
            document.write ("Please use the format Last name, first name, middle initial");
        }else{
            //output
            document.write ("Your name is: " +name);
        }
    }else{
        document.write ("Please use the format Last name, first name, middle initial");
    }
 </script>

But this is a not good design, because like what @Qantas94Heavy mention in your comment, if a user doesn't have a middle name or last name, your form will make it difficult for them to sign up.

Note: Also this is just a basic validation to make sure that the name has last name, first name and middle initial and the name is not longer than 20 characters as the OP mentioned. Of course if you want to be more accurate and advance you can use Regex to validate it again.

edited Dec 13, 2013 at 4:42

answered Dec 13, 2013 at 4:18

iCezz

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8 Comments

HardikS Over a year ago

name.length >=20 how does it make sure that each name is not longer than 20 characters ?

iCezz Over a year ago

He only mention name but not each name, assuming from his codes, he only has one input. AND if you think about it, will you have first name, middle name and last name with 20 characters each? I am quite amazed I got downvote for that.

HardikS Over a year ago

name.length >=20 will check for the at least 20 characters. if my firstname is 25 characters long, lastname is 30 characters long and intial is 15 characters then your condition will become true instead of false.

user3097967 Over a year ago

This doesn't seem to work, no matter how I format the name it comes back with the "Please use the format Last name, first name, middle initial" message. Am I missing something?

iCezz Over a year ago

Qantas94Heavy and @SpiderCode, apologised for not checking it throughly. Apparently my finger miss a few cm and hit the wrong key. edited my answer. Thanks for point it out.

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