Regular expression to match a number range in JavaScript

Question

I'm having problem with JavaScript regular expressions. I want to match real numbers form 1 to 5. Precission is in two digits. My code is but it doesnt work.

function validate_prosjek(nmb)
{
    var pattern= new RegExp(/[1-4]\.[0-9][0-9]|5\.00/);

    return pattern.test(nmb);
}

It recognizes real numbers higher than 5.

Please note that none of that has anything to do with jQuery, this is all Javascript functionality. This information should help you search for what you're looking for next time. — Steven Lu
– Steven Lu, Commented Apr 23, 2013 at 22:16
@RobertHarvey it can't work - it's not restrictive enough and will fail to ignore any extra numeric digits on either end of the number. — Alnitak
– Alnitak, Commented Apr 23, 2013 at 22:18

Alnitak · Accepted Answer · 2013-04-23 22:21:39Z

2

You need to "anchor" your regexp with ^ and $ to match the beginning and end of the string, respectively:

var pattern = /^([1-4]\.[0-9][0-9]|5\.00)$/;

You also need to escape the . because it's a special character in regexps, and there's no need to call new RegExp if the regexp is already in /.../ synax.

edited Apr 23, 2013 at 22:21

answered Apr 23, 2013 at 22:13

Alnitak

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8 Comments

Alnitak Over a year ago

@MikeM ok, so it does - I found a test case where it didn't work.

Bodo Hombah Over a year ago

/^[1-4]\.[0-9][0-9]|^5\.00$/

Bodo Hombah Over a year ago

Final version.Works fine. Your fail on cases where second digit is 5 and number is grater than 10, such as 15.00 25.00 and so long

Alnitak Over a year ago

@BodoHombah no, like Ansgar and MikeM pointed out, you need a group around the two alternatives.

Alnitak Over a year ago

the version that's been there for the last five minutes does not have that problem. You must have the () group.

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