regex pattern validation in HTML

Question

I want to validate a text box that should not have

Spaces in the beginning
All spaces
Spaces in the end

Here is the textbox code:

<input type="text" id="username" name="username" placeholder="Username..." required="required">

I can't use trim because of the implementation of the code is a bit complex, It would break other functionality. This is only a carry over project to me. So I decided to filter it out on the HTML textbox it self. But I don't know how to do this.

Update:

By the way I'm asking for a regex pattern.

Like this: jsfiddle.net/njUSJ ?

Passerby
– Passerby

2013-10-14 03:00:09 +00:00
Commented Oct 14, 2013 at 3:00 — Passerby
– Passerby, Commented Oct 14, 2013 at 3:00
@Passerby That would do it.

user764357
– user764357

2013-10-14 03:01:54 +00:00
Commented Oct 14, 2013 at 3:01 — user764357
– user764357, Commented Oct 14, 2013 at 3:01
If you enter only one character, it is invalid

newbie
– newbie

2013-10-14 03:05:13 +00:00
Commented Oct 14, 2013 at 3:05 — newbie
– newbie, Commented Oct 14, 2013 at 3:05

Mike Samuel · Accepted Answer · 2013-10-14 03:08:09Z

3

^\S(?:[\s\S]*\S)?$

should do it.

Translated into English, it's

^\S - starts with a non-space character

(?:...)?$ - optionally followed by ... which continues to the end of input

[\s\S]*\S - any number of any character, followed by a non-space character

answered Oct 14, 2013 at 3:08

Mike Samuel

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9 Comments

Havenard Over a year ago

Isn't [\s\S] the same as .?

ddmps Over a year ago

@Havenard . will does not include a new-line - [\s\S] does.

Havenard Over a year ago

Afaik \s matches newlines too. At least with the /s flag, but I guess it depends on the implementation.

Mike Samuel Over a year ago

@Havenard, no . and [\s\S] are not the same. HTML5 specifies regexs in terms of the EcmaScript spec, which defines . as "Atom :: . evaluates as follows: 1. Let A be the set of all characters except LineTerminator".

Mike Samuel Over a year ago

@Havenard, there is no /s flag in EcmaScript which is the controlling spec per HTML5 which says "The pattern attribute ... If specified, the attribute's value must match the JavaScript Pattern production."

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