How to use javascript regex to check for "empty" form fields?

Question

I am working on a php+javascript based project and have already made up a mockup page at : my website

I knew how to use javascript or php to check whether a particular field of form is "empty"or not, that is, whether it contains alphanumerical characters other than whitepsace characters(for instance, space, tab and newline).

However, my normal apporach no longer works since the jquery plugin that I am using now relies on regex to validate the fields.

If you go to the third tab(3. Fill up Shipping Info and Make Payment), you can enter something into the Firstname field and it does the check automatically. Fine. However, if you just simply put some space characters there and jump to the next field, well, it still feels okay for that, which is not correct since no one's first name is nothing!

The problem? At the back it has a regex like this :

"noSpecialCaracters":{
                    "regex":"/^[0-9a-zA-Z ]+$/",
                    "alertText":"* No special caracters allowed"},

This would not filter out empty characters.

I searched online and tried my best to make up another regex to match, I tried

"regex":"/^[^]+$/"

for matching non-empty characters, but that will not do...

Can anyone help me out? Many thanks in advance!

Which validation plugin are you using? If it's bassistance's Validation, it has a JSON property you can pass in. Usage: required: true — alex
– alex, Commented Feb 12, 2010 at 3:20
Hi Alex, this is the plugin page : position-absolute.com/articles/… — Michael Mao
– Michael Mao, Commented Feb 12, 2010 at 3:23

Nick Craver · Accepted Answer · 2013-08-22 09:45:50Z

23

Try this for non-whitespace:

([^\s]*)

Example:

/([^\s])/.test("   A"); //TRUE
/([^\s])/.test("    "); //FALSE

edited Aug 22, 2013 at 9:45

user2454455

answered Feb 12, 2010 at 3:17

Nick Craver

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5 Comments

Michael Mao Over a year ago

Hi Nick: I tried [code] "regex":"/^([^\s]*)$/", [/code] and [code] "regex":"/^[^\s]*$/", [/code] but neither works. Sorry I am not pro in regex at all...

Michael Mao Over a year ago

Hi Nick: Yeah that works for a vanilla javascript. But for the plugin... it still won't do. That's not the regex probelm I think. Probably something wrong in other places. thanks for your help!

Nick Craver Over a year ago

@Michael - I'll grab that plugin and test in the morning, check your SO messages at lunch tomorrow, this has me curious.

Michael Mao Over a year ago

@Nick : Thank so much for this. And plz take your time. I am not worried about this :)

Nick Craver Over a year ago

@Michael - The problem is the plugin fails to re-validate in some cases, not sure the route you want to take on fixing that. I'm using the jquery.validate plugin that's a bit more mature...you can do the same stuff, you'd only need to stick in some errorPlacement code to make it a bit fancier on display.

anonymous · Accepted Answer · 2011-06-03 08:20:41Z

12

function anyChar(str){
    return /\S+/.test(str);
}

will return false if emty data

answered Jun 3, 2011 at 8:20

anonymous

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Comments

Charles Wood · Accepted Answer · 2013-04-11 19:11:34Z

2

I'm using

/^\s*\S+.*/

which means

zero or more whitespace characters (\s*), followed by
one or more non-whitespace characters (\S+), followed by
anything at all, whitespace or not (.*).

This allows a single word or multiple words. I'm allowing whitespace at the beginning because I know how easy it is to miss a single space at the beginning and be really confused as to why your input isn't allowed :|

The Mozilla Developer Network has a great JavaScript regex page for reference.

answered Apr 11, 2013 at 19:11

Charles Wood

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Comments

Nick Bedford · Accepted Answer · 2010-02-12 03:23:20Z

1

You may want to try wrapping your expression in the following ^\s*(expression)\s*$. Then use the groups to find the "trimmed" matches. This eliminates only trailing or leading whitespace.

You can force the user to enter trimmed text or you can gracefully accept untrimmed input (better) as I find copying and pasting text often leaves some trailing or leading whitespace which the user may be unaware of.

answered Feb 12, 2010 at 3:23

Nick Bedford

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Comments

too much php · Accepted Answer · 2010-02-12 03:30:29Z

1

To answer your question, the minimal regex is /\S/ which will match as long as there is at least one non-whitespace character.

However, you probably don't want someone to put in a first name of '12345' or '!!!', so it might be better to use /[a-z]/i as this regex will only match if there is at least one alphabetical character.

answered Feb 12, 2010 at 3:30

too much php

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Comments

Charles Ma · Accepted Answer · 2010-02-12 03:39:53Z

1

/^\s*[0-9a-zA-Z][0-9a-zA-Z ]*$/

that ensures that at least one character is not whitespace and is of one of the allowed characters.

You may also want to consider other characters like hyphen(-) or apostrophe(') that may also appear in names...

/^\s*[0-9a-zA-Z][0-9a-zA-Z '-]*$/

edited Feb 12, 2010 at 3:39

answered Feb 12, 2010 at 3:24

Charles Ma

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2 Comments

Michael Mao Over a year ago

Hi Charles: It is true that I can force the user not to enter any leading whitespaces and that would certainly help me in this case. However, I still want to know how to walk around this problem, with the help from you guys, of course.

Charles Ma Over a year ago

well, if you want them to be able to have leading whitespace then this should do it /^\s*[0-9a-zA-Z][0-9a-zA-Z ]*$/

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