正则表达式，JavaScript中输入字符串中包含可选元素

Question

Can anyone give me the regular expression for currency which have the following formats :

1000 - valid
1,000 - valid
1,000.00 or 1000.00 - valid.

This means, the number May or May Not contain a comma(,) separator every 3 digits.

The number May Or May Not contain a dot (.), and if it carries a dot(.) it should show atleast 1 number after the decimal place.

And lastly it should be numerical characters only. If I need to make my question clear kindly suggest.

Answer 1

/^\d{1,3}(?:(?:,\d{3})*|(?:\d{3})*)(?:\.\d{1,2})?$/

"Between one and three digits, then any number of groups of three digits prefixed by a comma or any number of groups of three digits not prefixed by said comma (disallowing a mix of the two kinds of groups), then an optional group of one or two digits prefixed by a dot."

Note: This regex assumes that you want to validate an entire string against the criteria outlined in your question. If you want to use it to find such numbers in a longer string, you will need to remove the ^ and $ from the beginning and end of the expression.

Answer 2

Something like so should work: (,?\\d{3})+(\\.\\d{2})? . The regex will attempt to match a sequence of 3 digits precedeed by an optional comma, which is then, finally followed by an optional decimal point and 2 digits.

Please refer to this tutorial for more information.

EDIT: As per the comment below, the above regex can fail. I would recommend first using this regular expression: ^[\\d][\\d.,]+$ to make sure that you only have digits, thousand and decimal seperators. This regular expression will also make sure that the number starts with a digit, not with anything else. You could most likely have one regular expression which does everything, but it will most likely be quite complex.