Regular expression to validate a field

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I have an input in the form that should accept only the following formats:

Examples

  • 1AB
  • 1AB2CD
  • 1AB2CD3EF

The minimum size has to be 3 and the maximum 9, and always follow the standard 1 digit and 2 letters. It should not be accepted for example 1AB2 or 1AB2C.

I did so:

[0-9]{1}[a-zA-Z]{2}

But in this case only works for the first example I put, I do not know how to repeat the pattern.

jquery html5 regex
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    Do you have any code you have started to write to try to solve your problem? Show it to us.

  • I did so: [0-9]{1}[a-za-Z]{2} But in this case only works for the first example I put, I do not know how to repeat the pattern

1 answer

1


If you want the "1 digit, 2 letters" pattern to repeat at most 3 times, you can use the quantifier {}, indicating the minimum and maximum amount of times. In case, the minimum is 1, and the maximum is 3, then would be:

(\d[a-zA-Z]{2}){1,3}

Notice that I changed [0-9] for \d, for are equivalent* (both serve for digits). And removed the {1} because it’s redundant, since "1 repeat" is the standard ([0-9]{1} is the same as [0-9]).

And the parentheses are necessary, since the whole set "1 digit, 2 letters" must be repeated 1 to 3 times.

You can see this regex working here.

* Generally [0-9] and \d are equivalent. The only detail is that depending on the language/engine/configuration, the \d may also correspond to other characters representing digits, such as the characters ٠١٢٣٤٥٦٧٨٩ (see this answer for more details).

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