Query on Javascript RegEx

Question

I need a regex that allows 0-9, a-z, A-Z, hyphen, question mark and "/" slash characters alone. Also the length should be between 5 to 15 only.

I tried as follows, but it does not work:

var reg3 = /^([a-zA-Z0-9?-]){4,15}+$/;
alert(reg3.test("abcd-"));

If you want between 5 and 15, why did you write {4,15}? Also, what is {4,15}+ supposed to mean? The + means {0,}, it's not needed. — gen_Eric
– gen_Eric, Commented May 8, 2014 at 14:57
Try some online regex editor, it will help you learn quicker because you can play with the regex. refiddle is an example. — kapa
– kapa, Commented May 8, 2014 at 15:00

Ry- · Accepted Answer · 2014-05-08 14:57:47Z

4

length should be between 5 to 15 only

Is that why you have this?

{4,15}+

Just use {5,15}; it’s already a quantifier, and a + after it won’t work. Apart from that, the group isn’t necessary, but things should work.

/^[a-zA-Z0-9?/-]{5,15}$/

(I also added a slash character.)

answered May 8, 2014 at 14:57

Ry-♦

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Comments

Pedro Lobito · Accepted Answer · 2014-05-08 15:05:43Z

This is what you need:

if (/^([a-z\/?-]{4,15})$/i.test(subject)) {
    // Successful match
} else {
    // Match attempt failed
}

REGEX EXPLANATION

^([a-z\/?-]{4,15})$

Options: Case insensitive

Assert position at the beginning of the string «^»
Match the regex below and capture its match into backreference number 1 «([a-z\/?-]{4,15})»
   Match a single character present in the list below «[a-z\/?-]{4,15}»
      Between 4 and 15 times, as many times as possible, giving back as needed (greedy) «{4,15}»
      A character in the range between “a” and “z” (case insensitive) «a-z»
      The literal character “/” «\/»
      The literal character “?” «?»
      The literal character “-” «-»
Assert position at the very end of the string «$»

Ejaz · Accepted Answer · 2014-05-10 08:36:08Z

0

Couple issues,

you need {5,15} instead of {4,15}+
need to include /

Your code can be rewritten as

var reg3 = new RegExp('^[a-z0-9?/-]{5,15}$', 'i'); // i flag to eliminate need of A-Z
alert(reg3.test("a1?-A7="));

Update

Let's not confuse can be with MUST be and concentrate on the actual thing I was trying to convey.

{4,15}+ part in /^([a-zA-Z0-9?-]){4,15}+$/ should be written as {5,15}, and / must be included; which will make your regexp

/^([a-zA-Z0-9?/-]){5,15}$/

which CAN be written as

/^[a-z0-9?/-]{5,15}$/i   // i flag to eliminate need of A-Z

Also I hope everybody is OK with use of /i

edited May 10, 2014 at 8:36

answered May 8, 2014 at 15:02

Ejaz

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3 Comments

gen_Eric Over a year ago

You know you can do var reg3 = /^([a-z0-9?\-]){5,15}$/i;, right? You don't need to use new RegExp.

Ejaz Over a year ago

Yes that's true (and I know).

Ry- Over a year ago

Can be rewritten? Sure, but it’s not better. new RegExp is inappropriate on static strings.

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