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

Posted on 2009-05-04
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

Question by:Samm1502
LVL 84

Accepted Solution

ozo earned 250 total points
ID: 24293552
/[0-9]{1,2}/ can match either the first 88 or the last 88 in "888"
would only allow . and not 8 after the first 88

Expert Comment

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.


Author Comment

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.
LVL 35

Assisted Solution

by:Terry Woods
Terry Woods earned 250 total points
ID: 24299178
In ozo's solution
the ^ matches the start of the string.

Altering it to restrict it to 1 or 2 digits after the decimal would be:

$ matches the end of the string.

Author Closing Comment

ID: 31577483
Thanks for the explanation. Cheers Sam

Featured Post

Three Reasons Why Backup is Strategic

Backup is strategic to your business because your data is strategic to your business. Without backup, your business will fail. This white paper explains why it is vital for you to design and immediately execute a backup strategy to protect 100 percent of your data.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
count 1s in access 2016 6 54
RegEx help in C#.NET 8 55
Validate textbox with client generated button 6 64
Regular expressions Exclude patter 3 37
Whatever be the reason, if you are working on web development side,  you will need day-today validation codes like email validation, date validation , IP address validation, phone validation on any of the edit page or say at the time of registration…
As most anyone who uses or has come across them can attest to, regular expressions (regex) are a complicated bit of magic. Packed so succinctly within their cryptic syntax lies a great deal of power. It's not the "take over the world" kind of power,…
Learn how to match and substitute tagged data using PHP regular expressions. Demonstrated on Windows 7, but also applies to other operating systems. Demonstrated technique applies to PHP (all versions) and Firefox, but very similar techniques will w…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question