正则表达式-如何匹配小于或等于二十四的所有数字？

Question

I'm somewhat new to regular expressions and am writing validation for a quantity field where regular expressions need to be used.

How can I match all numbers less than or equal to 24?

I tried

var pat = /^[1-9]$|^[1-2]\d$|^3[0-6]$/;

But that only matches 1-24. Is there a simple way to match all possible numbers less than or equal to 24?

Answer 1

I won't recommend you to use regex just to check if a number is between the range. To compare the numbers comparison operators should be used.

if (number >= 0 && number <= 24)

However, if this is not feasible/possible, you can use regex.

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You can also use

^(2[0-4]|[01]?[0-9])$

Regex101 Demo

Explanation:

1. ^ : Start of line anchor
2. 2[0-4] : Matches 2 followed by any number between 0 to 4 - Matches 20-24
3. | : OR condition in regex
4. [01]?[0-9] : [01]? : Matches 0 or 1 optionally. [0-9] : Matches any number exactly once in the range 0 to 9 - Matches 0-19

Demo

 input:valid { color: green; } input:invalid { color: red; } 

 <input pattern="(2[0-4]|[01]?[0-9])" /> 

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You can use following regex

^(2[0-4])|(^[01]?[0-9])$

Regex101 Demo

Answer 2

^(?:[0-9]|[1][0-9]|2[0-4])$

Try this.See demo.

https://regex101.com/r/iJ7bT6/3