I'm trying to get a regex for an amount:

ANY DIGIT + PERIOD (at least zero, no more than one) + ANY DIGIT (at least zero no more than two [if possible, either zero OR two])

What I have is:

/^\d+\.\{0,1}+\d{0,2)+$/

...obviously not working. Examples of what I'm trying to do:

123 valid

123.00 valid

12.34.5 invalid

123.000 invalid

Trying to match an amount with or without the period. If the period is included, can only be once and no more than two digits after.

I'm trying to get a regex for an amount:

ANY DIGIT + PERIOD (at least zero, no more than one) + ANY DIGIT (at least zero no more than two [if possible, either zero OR two])

What I have is:

/^\d+\.\{0,1}+\d{0,2)+$/

...obviously not working. Examples of what I'm trying to do:

123 valid

123.00 valid

12.34.5 invalid

123.000 invalid

Trying to match an amount with or without the period. If the period is included, can only be once and no more than two digits after.

• javascript
• regex

• There are usually much better ways to detec a number. parseFloat for instance. – Madara's Ghost Commented Oct 7, 2011 at 16:01
• @RikudoSennin parseFloat can be used as an attempt to convert a string to a number, possibly resulting in NaN, or an unwanted number. RegExps can be used to validate the string. – Rob W Commented Oct 7, 2011 at 16:03
• Yes, though if parseFloat return a NaN that would probably mean that it's not a valid number. – Madara's Ghost Commented Oct 7, 2011 at 16:06

3 Answers 3

Make the decimal point and 1 or 2 digits after the decimal point into its own optional group:

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

Tests:

> var re = /^\d+(\.\d{1,2})?$/
  undefined
> re.test('123')
  true
> re.test('123.00')
  true
> re.test('123.')
  false
> re.test('12.34.5')
  false
> re.test('123.000')
  false

Have you tried:

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

The ? makes the group (\.\d{1, 2}) optional (i.e., matches 0 or 1 times).

Would something like this work?

// Check if string is currency
var isCurrency_re    = /^\s*(\+|-)?((\d+(\.\d\d)?)|(\.\d\d))\s*$/;
function isCurrency (s) {
   return String(s).search (isCurrency_re) != -1
}