Question

I’m trying to write a regular expression in JS to recognize any digit up to seven times, followed by a “-” followed by 2 digits followed by “-” followed by a single digit. This is the simple regex I have:

/\d{1,7}-\d{2}-\d/g

This should match strings like:

• 123-12-7
• 1-12-7
• 1234567-12-7

but not 12345678-12-1

However, the above is returning true. The regex returns true when there is any number of digit in the first group.

Does the JavaScript Regex object not support {n,m}?

Here is an example of what I am talking about.

var pattern = new RegExp(/\d{1,7}-\d{2}-\d/);
alert(pattern.test("12345678-13-1"));

http://jsfiddle.net/XTRAc/1/ live example

Answer 1

It matches 2345678-13-1. You need to anchor it to the beginning and end of your string:

/^\d{1,7}-\d{2}-\d$/

Note though, that (as Rocket Hazmat pointed out) you do not need to use the RegExp constructor if you use a regex literal (something without string quotes).

JSFiddle