Regular Expression inner Digits check

Question

I have the following regex but it fails (the inner digits with the points) :

([0-9]{1,3}\.?[0-9]{1,3}\.?[0-9]{1,3})

I want that it covers the following cases:

• 123 valid
• 123.4 valid
• 123.44 valid
• 123.445 valid
• 123.33.3 not ok (regex validates it as true)
• 123.3.3 not ok (regex validates it as true)
• 123.333.3 valid
• 123.333.34 valid
• 123.333.344 valid

Can you please help me?

Answer 1

You have multiple case, I would like to use | the or operator like this :

^([0-9]{1,3}|[0-9]{1,3}\.[0-9]{1,3}|[0-9]{1,3}\.[0-9]{3}\.[0-9]{1,3})$
^           ^                      ^                                 ^

you can check the regex demo

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details

The regex match three cases :

case 1

[0-9]{1,3}

this will match one or more digit

case 2

[0-9]{1,3}\.[0-9]{1,3}

this will match one or more digit followed by a dot then one or more digits

case 3

[0-9]{1,3}\.[0-9]{3}\.[0-9]{1,3}

this will match one or more digit followed by a dot then three digits then a dot then one or three digits

Note you can replace [0-9] with just \d your regex can be :

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