Javascript: How to retrieve the number of decimals of a *string* number?

Question

I have a set of string numbers having decimals, for example: 23.456, 9.450, 123.01... I need to retrieve the number of decimals for each number, knowing that they have at least 1 decimal.

In other words, the retr_dec() method should return the following:

retr_dec("23.456") -> 3 retr_dec("9.450")  -> 3 retr_dec("123.01") -> 2 

Trailing zeros do count as a decimal in this case, unlike in this related question.

Is there an easy/delivered method to achieve this in Javascript or should I compute the decimal point position and compute the difference with the string length? Thanks

Answer 1

function decimalPlaces(num) {   var match = (''+num).match(/(?:\.(\d+))?(?:[eE]([+-]?\d+))?$/);   if (!match) { return 0; }   return Math.max(        0,        // Number of digits right of decimal point.        (match[1] ? match[1].length : 0)        // Adjust for scientific notation.        - (match[2] ? +match[2] : 0)); } 

The extra complexity is to handle scientific notation so

decimalPlaces('.05') 2 decimalPlaces('.5') 1 decimalPlaces('1') 0 decimalPlaces('25e-100') 100 decimalPlaces('2.5e-99') 100 decimalPlaces('.5e1') 0 decimalPlaces('.25e1') 1