Regex - Creating An Input/textarea That Correctly Interprets Numbers

Im designing a conversion website where i perform calculations on inputted numbers and i need my input or textarea to receive and interpret numbers entered in different fashions l

Solution 1:

I believe this should handle everything:

^[1-9](?:\d{0,2}(?:([,.])\d{3})*|\d+)(?:(?!\1)[,.]\d+)?$

You're treading on complicated territory here. Also, the above RegEx does not allow for values less than "1".

Basically, the RegEx does the following:

1. Allows for no thousandths separators ("," or ".") but ensures if they are used that they occur in the correct places.
2. Allows for either "," or "." to be used as both thousandths/cents separators, but ensures that the cents separator is not the same as the thousandths separator.
3. Requires the string equivalent number to begin with any digit other than "0".

To implement this you could attach an event listener to your form element(s) and use JS to do a simple .test.

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After reading further, I think I misinterpreted your goal originally. I assumed you simply wanted to validate these values with a RegEx. I also assumed you're trying to work with currency (ie. two decimal places). However, fret not! You can still utilize my original answer if you really want.

You mentioned input and textarea which are both form elements. You can attach a listener to these element(s) looking for the input, change, and/or keyup events. As a part of the callback you can run the .test method or some other functionality. Personally, I would rethink how you want to handle input. Also, what's your actual goal here? Do you really need to know the thousandths separator or keep track of it? Why not just disallow any characters other than the one decimal point/comma and digits?

Also, parsing numbers like .0000000001 as a float is a terrible idea. You will lose precision very quickly if you do any sort of calculations such as multiplication, division, power, etc. You're going to have to figure out a different method to do this like storing the number to the right separately and as integers instead then go from there.

I can help you if you describe what you're trying to do in better detail.