RegEx for currency (JavaScript)

Question

I am new to regular expressions and i would like to validate user input with javascript.

The user input is a currency, but i want it without the thousands commata.

Valid

"12.34"
"12,34"
"1234,5"
"123"
"123,00"
"12000"

Invalid

"12a34"
"abc"
"12.000,00"
"12,000.00"

I tried the following regex-pattern, but it doesnt work for me. it validates for example "12a34" and i dont know why.

/\d+([\.|\,]\d+)?/

What would be the correct regex-pattern ? Could you explain this step by step ?

Thanks !

Answer 1

Do not escape the . while in a character group. Try with following regex:

/^\d+([.,]\d{1,2})?$/

^   = start of string
$   = end of string
()? = an optional capturegroup ( e.g. to validate "123")
{x,y} = The symbol may occur minimum x and maximum y times

Answer 2

RegExp: /^(?!\(.*[^)]$|[^(].*\)$)\(?\$?(0|[1-9]\d{0,2}(,?\d{3})?)(\.\d\d?)?\)?$/g
pattern: ^(?!\(.*[^)]$|[^(].*\)$)\(?\$?(0|[1-9]\d{0,2}(,?\d{3})?)(\.\d\d?)?\)?$
flags: g
3 capturing groups: 
   group 1: (0|[1-9]\d{0,2}(,?\d{3})?)
   group 2: (,?\d{3})
   group 3: (\.\d\d?)

Regex Test