With JavaScript, I need help concatenating a variable into a regular expression

Question

I'm writing a JavaScript function to extract a segment out of a URL that appears to the right of a designated segment.

For instance, if this is my URL ...

mysite.com/cat/12/dog/34?test=123

... I would like to be able to pass 'cat' to the function and get 12, and later pass 'dog' to the function and have it return 34. I found this answer on StackOverflow to extract the URL segment, but it uses a string literal. And I'm having difficulty concatenating a passed in value.

jQuery to parse our a part of a url path

Here is my code. In this, rather than hard coding 'cat' into the pattern match, I would like to pass 'cat' into the segmentName parameter and have the regular expression match on that.

var url = "www.mysite.com/cat/12/dog/34?test=123";
alert(getNextSegmentAfterSegmentName(url, 'cat'));

function getNextSegmentAfterSegmentName(currentPath, segmentName) {
   var nextSegment = "";
   segmentName = segmentName.toLowerCase();
   //var currentPath = window.location.pathname.toLowerCase();
   if (currentPath.indexOf(segmentName) >= 0) {
      var path = currentPath.split('?')[0]; // Strip querystring

      // How do I concatenate segmentName into this?
      var matches = path.match(/\/cat\/([^\/]+)/);

      if (matches) {
         nextSegment = matches[1];
      }
   }
   return nextSegment;
}

Here is a jsfiddle example: http://jsfiddle.net/Stormjack/2Ebsv/

Thanks for your help!

Rohit Jain · Accepted Answer · 2013-11-21 16:50:25Z

1

You need to create a RegExp object if you want to create regex using some string variable:

path.match(new RegExp("\/" + segmentName + "\/([^\/]+)"));

answered Nov 21, 2013 at 16:50

Rohit Jain

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