RegExp在小数点后三位放置零（0）

Question

Hi all i need all these possible cases to be valid

0.001
0.320
0.009
0.0
0.3
0.9

let reqDecimal=/^(0(.\\d+)?|1(.0+)?)$/; I tried above code need to expected 3 decimal values not more than.

Answer 1

Simply replace both of your plus signs with {1,3) :

/^(0(.\d{1,3})?|1(.0{1,3})?)$/

This ensures that there are between 1 and 3 digits between each decimal:

 const regex = /^(0(.\\d{1,3})?|1(.0{1,3})?)$/; const amounts = [ "0.001", "0.320", "0.009", "0.0", "0.3", "0.9", "0.", "0.0000", "1.", "1.000", "1.0000" ] amounts.forEach(function(amount) { console.log(amount, "=", regex.test(amount)); }); 

This can also be seen working on Regex101 here .

Answer 2

You could probably use:

^(?:1|0)\.\d{1,3}$

If you are wanting to stay at or under 1.000 :

^0\.\d{1,3}\b|1\.0{1,3}\b$

Examples :

https://regex101.com/r/wKZseY/1
https://regex101.com/r/wKZseY/2