需要這個正則表達式來檢查3個小數位嗎？

Question

我：

^-?[0-9]\d*(\.\d+)?$ 

但需要它，只允許最多3位小數。所以允許值包括：

+10.123 

-10.123 

10.123 

10 

+10 

-10 

10.1 

10.12 

不允許：

10.1234 

10.123% 

通知/提示理解表達MODS的。

在此先感謝。

Answer 1

^[+-]?\d+(\.\d{1,3})?$ 

說明：

見這裏：https://www.debuggex.com/r/BbCBL5pQWLxsD4a6

^ asserts position at start of a line 
    Match a single character present in the list below [+-]? 
    ? Quantifier — Matches between zero and one times, as many times as possible, 
        giving back as needed (greedy) 
    +- matches a single character in the list +- (case sensitive) 
    \d+ matches a digit (equal to [0-9]) 
     + Quantifier — Matches between one and unlimited times, as many times as possible, 
        giving back as needed (greedy) 
    1st Capturing Group (\.\d{1,3})? 
    ? Quantifier — Matches between zero and one times, as many times as possible, 
        giving back as needed (greedy) 
    \. matches the character . literally (case sensitive) 
    \d{1,3} matches a digit (equal to [0-9]) 
    {1,3} Quantifier — Matches between 1 and 3 times, as many times as possible, 
         giving back as needed (greedy) 
    $ asserts position at the end of a line 

說明來自：https://regex101.com/]

Answer 2

^[+-]{0,1}\d*?(\.{0,1}\d{0,3})?$應該工作

看到https://regex101.com/r/P6DBrW/1/的正則表達式

Answer 3

除了*和+元字符，它指定無限重複的說明，正則表達式允許您將在比賽用一些具體的限制{a,b}構造。在此，a是所需的最小匹配數，而b是最大值。 a和b均爲，包括。

既然你需要搭配最多三個數字至少一個，你需要\d{1,3}更換\d+：

^[+-]?[0-9]\d*(\.\d{1,3})?$ 

優化：在手工作正則表達式，您可以通過更換[0-9]優化與另一\d，和 「摺疊」 成\d*通過使用\d+：

^[+-]?\d+(\.\d{1,3})?$ 

Answer 4

^(?!0\d)\d*   
(\.\d{1,4})?$