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Javascript length limit of regex with given decimal conditions

I could make Javacsript regex with 2 decimal points with 3 integer but the thing is I have to make it 6 digits total including the decimal "dot".
So this result should be a minimum 0 to 999.99 with the condition it's a minimum 0 to 6 digit length.
Below is my solution So far:
^(\d{0}(?:\d{1,3})|\d{1}\.(?:\d{1,2})|\d{2}\.(?:\d{1,2})|\d{3}\.(?:\d{1,2}))$
Explanation:
If it's 0 digits, then min 1 to 3 digits so I can make it max 999.
If it's 1 digit w/ decimal then max 2 decimal points (ex) 2.22
If it's 3 digits w/ decimal then max 2 decimal points. (ex) 3.33
This is for regex in my JSP input (which is text type) and I'm literally suffering for this problem for days.
(this regex is for versions to be specific..)
Any help or better alternative way would help me A LOT.
google search, try by myself, online course, Youtube

If I get it well: you need to match a decimal with a length of 6 including the decimal point.
The following can do:
^(\d{1,3}(?:\.\d{1,2})?)$
It specified a integer part up to 3 digits, then an optional decimal part.
It has some edge cases of course such as matching: 000.00 which can be cleaned up further if needed depending on your expected input.
Sample: https://regex101.com/r/LrOHvt/1

Javascript regex positive less than 10000 than can be decimal

I need a regex for a number than can be decimal and less than 10000 with max 2 digits after decimal.
I tried
/^([0-9]{1,4})+(\.[0-9]{0,2})$/
but it returns true for 44555.54 for example.

In your regex you are using + which is using for one or more repetition and which leads to match any length of digit and make decimal part non-greedy(using?) to make it optional.
^[0-9]{1,4}(\.[0-9]{0,2})?$
or using \d for digit character class.
^\d{1,4}(\.\d{0,2})?$

Regular Expression For Decimal with precision 5 and scale 2

I am trying to validate a text box on key press and here is my criteria.
I need a regular expression which allows total of 5 digits and a decimal point.
If there's no decimal point then it should allow to enter 5 digits.
And if there's a decimal point then it should allow only 2 digits after the decimal point.
However the total number of digits should not exceed 5 digits excluding decimal point and it can be less than 5 digits.
And below is my regex
/^(?:\d{1,2}(?:\.\d{0,6})?)?$/
I hope I am clear and let me know if any clarifications needed
Please help Thanks in advance.

Here's a regex that just lists out alternatives separated by |:
/^\d{1,5}|\d{1,4}\.\d|\d{1,3}\.\d{2}$/
i.e.
1-5 digits with no decimal point OR 1-4 digits followed by a decimal point and one digit after the decimal OR 1-3 digits followed by a decimal point and two digits after the decimal.

Regex to check amount is greator then one

I have a regex
^(?=.*[1-9])\\d{0,5}(?:\\.\\d{0,2})?$
to check amount should be greater then 0 and it can contain maximum five digit before decimal and optional decimal and 2 digits after decimal.
Here (?=.*[1-9]) is to check there should be latest one occurrence of any digit from (1-9) in the string.
But I want modify it to check amount greater then one(1), so I want (?=.*[1-9]) to check only till the occurrence of the decimal point i.e. 0.1 it should return false.
Other condition should also fulfill.
Note : the count of digits before decimal is not fix, it will very from 1 to 5, so we can't modify it to (?=.{0,5}[1-9])

You can fix it by using this negation based regex:
^(?=[^.]*[1-9])\\d{0,5}(?:\\.\\d{0,2})?$
RegEx Demo
[^.]* before [1-9] will match any character except decimal point thus not allowing 0.45 as valid number.

What regex for jQuery satisfies these conditions?

I have a field for which can have:
Up to potentially 2 decimals places
Up to potentially 6 non-decimal places
No more than 8 digits altogether (the max 2 decimals plus max 6 non-decimals)
Be a positive number
So correct inputs would be range from 0.01 to 999999.99, and trailing zeroes isn't an issue, so 4.00 is just as fine as 4.

Try this pattern:
^[0-9]{1,6}(?:\.[0-9]{1,2}0*)?$
If you want to allow leading and trailing whitespace, add \s* to the beginning and the end of the pattern, right after ^ and right before $.
That said, this task is something you might want to accomplish without regex. Why don't you just read the value of the input, parse it and then simply perform a numeric validation? You could even round the input to two decimal places.

You could try something like so:
Up to potentially 2 decimals places: (\.\d{1,2})? - This will match a decimal point followed by a minimum of 1, and a maximum of 2 digits. This is optional.
Up to potentially 6 non-decimal places: \d{1,6} - This will match a minimum of 1 digit and a maximum of 6 digits.
No more than 8 digits altogether (the max 2 decimals plus max 6 non-decimals): You can combing the two above to get this: \d{1,6}(\.\d{1,2})?.
Be a positive number: Change the above to this: ^\d{1,6}(\.\d{1,2})?$. This should make sure that any number you pass to it, does not start with a negative sign. The ^ and $ anchors instruct the regex engine to start matching at the beginning of the string and complete the matching at the end. This should allow you to be sure that the string you are matching is indeed a number.
That being said, you should really be doing numerical range checks using the appropriate mathematical operations which your language (in this case JavaScript) provides. A small change in the numerical range you are after will most likely bring a large change in your regular expression.

This might validate it
# /^(?=.*[1-9].*$)(?=[.]?(?:\d[.]?){1,8}$)(?=\d{0,6}(?:[.]\d{0,2})?$)/
^
(?= # must be a positive number
.* [1-9] .* $
)
(?=
[.]?
(?: # 1 to 8 digits
\d
[.]?
){1,8}
$
)
(?=
\d{0,6} # 0 to 6 non-decimal places
(?:
[.] # 0 to 2 decimal places
\d{0,2}
)?
$
)