restrict the maximum character count in regex

Question

restrict the maximum character count in regex

The string can consist of a single number or multiple numbers separated by "-", but the total character count must not exceed 6.

Examples of valid strings

Examples of invalid strings

-3
6666-
5555-6666

My initial regex

/^\d+(-?\d+)?$/

However, the original regex considers '5555-6666' as valid even though it exceeds 6 characters in length.

I then attempted the following

/^(\d+(-?\d+)?){1,6}$/

Unfortunately, this interpretation groups all enclosed sets together and expects them to be between 1 and 6 in total.

So, how can we enforce the total character count limit with the described requirements using regex?

javascript regex

Answer 1

Answer №1

Approach 1 :-

The simplest method is to check the length before applying regex (I recommend using this approach that verifies the length first and then applies regex)

str.length < 7 && /^\d+(-?\d+)?$/.test(str)

Approach 2 :-

Another way is to utilize positive lookahead

^(?=.{0,6}$)\d+(-?\d+)?$

https://i.sstatic.net/QzwGC.png

Regex Demo

Answer 2

Approach 1 :-

The simplest method is to check the length before applying regex (I recommend using this approach that verifies the length first and then applies regex)

str.length < 7 && /^\d+(-?\d+)?$/.test(str)

Approach 2 :-

Another way is to utilize positive lookahead

^(?=.{0,6}$)\d+(-?\d+)?$

https://i.sstatic.net/QzwGC.png

Regex Demo

Answer 3

Answer №2

To enforce a maximum of 6 characters, you can utilize a positive lookahead pattern:

^(?=.{1,6}$)\d+(?:-\d+)?$

Example: https://regex101.com/r/kAxuZp/1

Alternatively, you can use a negative lookahead to prevent starting with a dash and another negative lookahead to avoid two consecutive dashes:

^(?!-)(?!.*-.*-)[\d-]{0,5}\d$

Example: https://regex101.com/r/kAxuZp/3

Answer 4

To enforce a maximum of 6 characters, you can utilize a positive lookahead pattern:

^(?=.{1,6}$)\d+(?:-\d+)?$

Example: https://regex101.com/r/kAxuZp/1

Alternatively, you can use a negative lookahead to prevent starting with a dash and another negative lookahead to avoid two consecutive dashes:

^(?!-)(?!.*-.*-)[\d-]{0,5}\d$

Example: https://regex101.com/r/kAxuZp/3

Answer 5

Answer №3

If you want to ensure that your current regex pattern works properly, you can also verify the length of the input without the dash:

var inputValue = "4444-1";
if (/^\d+(-?\d+)?$/.test(inputValue) && inputValue.replace("-", "").length <= 6) {
    console.log("MATCH");
}
else {
    console.log("NO MATCH");
}

It's important to note that checking the input length is most effective after removing the dash, as this allows us to accurately determine the total number of digits present.

Answer 6

If you want to ensure that your current regex pattern works properly, you can also verify the length of the input without the dash:

var inputValue = "4444-1";
if (/^\d+(-?\d+)?$/.test(inputValue) && inputValue.replace("-", "").length <= 6) {
    console.log("MATCH");
}
else {
    console.log("NO MATCH");
}

It's important to note that checking the input length is most effective after removing the dash, as this allows us to accurately determine the total number of digits present.

restrict the maximum character count in regex

Answer №1

Answer №2

Answer №3

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