Compare length of string in regex javascript

Question

I don't have much knowledge about working of regex but I have been trying to solve this from last many hours but could not get solution of it`.

regex  /^[]{13,17}$/i

I have a text-box and text-box value should be greater than or equal to 13 and less than or equal to 17.

Ex.

var value - "12345678901234".(textbox value and length is 14)
if (value.match(regex)) {
  alert("Correct value");
} else {
  alert("error");
}

Now, length is 14, it means condition should be true. But match function always return null. I have tried also test function, but it doesn't give desired result.

Hi Wiktor. This regex is coming from database and it's creating dynamically. In subscript, sometimes value can't be blank. — Puneet Chawla
– Puneet Chawla, Commented Feb 9, 2016 at 10:05
Then you have to replace dynamically [] by . ; check alert("1234567890123".match( /^[]{13,17}$/i) + " " + "1234567890123".match( /^.{13,17}$/i)) and you will see the difference. — Amessihel
– Amessihel, Commented Feb 9, 2016 at 10:10
This online regex expression builder might help. It displays errors and provides expression hints: https://regex101.com/ — Yogi
– Yogi, Commented Feb 9, 2016 at 10:12
If you actually mean any character, then you must replace [] with [^] or [\s\S]. Can you replace each [] with [\s\S]/[^]? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Feb 9, 2016 at 10:12

MaxP · Accepted Answer · 2016-02-09 10:10:02Z

3

You should specify which kind of characters has to be in the sequence:

Any character-

/^.{13,17}$/i

Digits -

/^[0-9]{13,17}$/i

Letters -

/^[A-Z]{13,17}$/i

letters, digits, underscore and dash -

/^[A-Z0-9_-]{13,17}$/i

answered Feb 9, 2016 at 10:10

MaxP

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5 Comments

MaxP Over a year ago

Hi Puneet - I agree with other comment contributions - if that regular expression is given, you need to change it dynamically (sorry, but when I started answering there was no comment).

Puneet Chawla Over a year ago

Okay. Can you please update your question with specifying how can i change it dynamically.

MaxP Over a year ago

I am not sure about your case, but you can convert the regexp to a string (toString()), strip the leading '/' and trailing '/i' away, then replace the squares with a dot replace( "[]", "." ) and eventually convert the string back to regexp (new RegExp( str, "i" ))

Puneet Chawla Over a year ago

It also doesn't work - Any character - /^.{13,17}$/i. Only this work ^.{13,17}$ but can't use this.

MaxP Over a year ago

I think you are mixing strings ("abc") and regexp (/abc/) concepts. If you invoke match with a string, then no slashes are needed, but if you use a regexp, then slashes are needed because they are the delimiters for the regexp itself. You can switch back and forth between regexp and string as I wrote in my comment above.

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