使用正则表达式评估数字

Question

I have a regex to evalute numbers

^\d*(?:,\d+)*(?:.\d+)?

These are some numbers to check it

12345 -- correct

.123 -- correct

23,456,789.123 --correct

123.456.7 -- wrong

1. -- wrong

12345, -- wrong

123., -- wrong

,123 -- correct

but this last test case should be wrong. It should not be correct. Any help is accepted thank you

Answer 1

Try this regex:

^(?!,|$)\d*(?:,\d+)*(?:\.\d+)?$

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Explanation:

• ^ - asserts the start of the line
• (?!,|$) - negative lookahead to make sure that the current position is not followed by either a , or end of the line
• \d* - matches 0+ occurrences of a digit
• (?:,\d+)* - matches 0+ occurrences of (a , followed by 1+ digits)
• (?:\.\d+)? - matches a . followed by 1+ occurrences of a digit. ? at the end makes this sub-sequence optional
• $ - asserts the end of the line