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How to get regular expresson ti limirt number of digits to be entered by user

Posted on 2009-05-04
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Last Modified: 2012-05-06
This would seem very simple because I only want my user to be able to enter up to 2 digits followed by a . char followed by up to 2 decimal places.

So in other words a floating point value such as 99.99 or 3.45 or 37.8 but not 888 or 888.88.

Now my Javascript regular expression to allow up to 2 digits before the floating point looks like this:

var regExp = /[0-9]{1,2}/

but what I don't understand is that this expression returns true when I call
regExp.test("888"); ?????

Can anyone explain this and tell me what I should be putting to ensure the 3rd digit causes an invalid result?

Many thanks
Sam

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Question by:Samm1502
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5 Comments
 
LVL 84

Accepted Solution

by:
ozo earned 1000 total points
ID: 24293552
/[0-9]{1,2}/ can match either the first 88 or the last 88 in "888"
/^[0-9]{1,2}\./
would only allow . and not 8 after the first 88
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LVL 9

Expert Comment

by:ghostdog74
ID: 24293750
yes its actually quite simple that you don't need a regular expression for that.  so according to this

>> So in other words a floating point value such as 99.99 or 3.45 or 37.8 but not 888 or 888.88.

you can
1) check whether the string has a decimal "." .
2) if there's decimal
     a) split the string on "." as delimiter.
     b) check 1st element and 2nd element whether they less than 99 and more than 0.


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Author Comment

by:Samm1502
ID: 24295105
Thanks ghostdog74 but I have to use a regular expressions for reasons I won't bore you with and ozo if I read this correctly it test for the existence of any char not in the range [0-9] but I need to make sure my regexp.test call returns true if the entered value is valid and false otherwise so how do I alter my original expression to prevent it matching part of the entered string and force it match all of it i.e. allwo just 1 or 2 digits before the . and 1 or 2 digits afterwards?

Many thanks.
Sam
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LVL 35

Assisted Solution

by:Terry Woods
Terry Woods earned 1000 total points
ID: 24299178
In ozo's solution
/^[0-9]{1,2}\./
the ^ matches the start of the string.

Altering it to restrict it to 1 or 2 digits after the decimal would be:
/^[0-9]{1,2}\.[0-9]{1,2}$/

$ matches the end of the string.
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Author Closing Comment

by:Samm1502
ID: 31577483
Thanks for the explanation. Cheers Sam
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