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

rated 0 times [ 152] [ 3] / answers: 1 / hits: 66777 / 12 Years ago, fri, may 4, 2012, 12:00:00

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

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krystadesiraeo

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2 Years ago

answered 12 Years ago kourtney · Accepted Answer

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

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

Answers

krystadesiraeo

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