regex - Decimal or numeric values in regular expression validation

Question

I am trying to use a regular expression validation to check for only decimal values or numeric values. But user enters numeric value, it don't be first digit "0"

How do I do that?

Answer 1

A digit in the range 1-9 followed by zero or more other digits:

^[1-9]d*$

To allow numbers with an optional decimal point followed by digits. A digit in the range 1-9 followed by zero or more other digits then optionally followed by a decimal point followed by at least 1 digit:

^[1-9]d*(.d+)?$

Notes:

• The ^ and $ anchor to the start and end basically saying that the whole string must match the pattern

• ()? matches 0 or 1 of the whole thing between the brackets

Update to handle commas:

In regular expressions . has a special meaning - match any single character. To match literally a . in a string you need to escape the . using . This is the meaning of the . in the regexp above. So if you want to use comma instead the pattern is simply:

^[1-9]d*(,d+)?$

Further update to handle commas and full stops

If you want to allow a . between groups of digits and a , between the integral and the fractional parts then try:

^[1-9]d{0,2}(.d{3})*(,d+)?$

i.e. this is a digit in the range 1-9 followed by up to 2 other digits then zero or more groups of a full stop followed by 3 digits then optionally your comma and digits as before.

If you want to allow a . anywhere between the digits then try:

^[1-9][.d]*(,d+)?$

i.e. a digit 1-9 followed by zero or more digits or full stops optionally followed by a comma and one or more digits.