regular expression to match Number + string

Question

I am trying to match these use cases in Javascript:
a) 8 Months
b) 18 Years

Numbers could range from 1 to 20 and the strings could only be either "months" or "years"

I am trying this

[0-9]\s(Years|Months)

But it is not working.

Try [0-9]+\s(Years|Months) + will make RE to accept atleast 1 number. — Jake Peralta
– Jake Peralta, Commented May 12, 2021 at 12:36

logi-kal · Accepted Answer · 2021-05-12 12:49:49Z

3

You can use this:

([1-9]|1[0-9]|20)\s(Years|Months)

where:

[1-9] matches a digit from 1 to 9
1[0-9] matches a number from 10 to 19
20 matches just 20

Edit: As noticed in a comment, you should use

^([1-9]|1[0-9]|20)\s(Years|Months)$

if the whole string must exactly match with this text.

Another option is prepending the regex with a word boundary (\b) in order to prevent matching cases like "42 Years".

edited May 12, 2021 at 12:49

answered May 12, 2021 at 12:37

logi-kal

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2 Comments

3limin4t0r Over a year ago

Note that this regex still matches 2 Years in the text 42 Years, depending on the context of OP you (the reader of the answer) might want to anchor the regex to the start ^ and end $ of the string or use a negative lookbehind to make sure the character before the match is not a number.

logi-kal Over a year ago

@3limin4t0r Thank you, I updated the answer mentioning also the word boundary.

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