Leveraging URL parameters in Express.js Routes

Within my routes directory for a node and Express.js web application, the code snippet below is causing a problem:

var router = express.Router();

router.get(htmlExt('index/:fileName'), function(req, res){
  console.log(req.params.fileName);
});

I'm facing an issue where req.params.fileName is only returning the first letter of the :fileName parameter. Despite thoroughly checking my code, I can't seem to identify what's causing this unexpected behavior. Any insights on how to resolve this?

node.jsexpressroutes

Answer №1

After careful analysis, it seems that the issue stemmed from the interpretation of the Express Router pattern.

  1. The journey began with /index/:fileName
  2. Next, htmlExt transformed this into 
    /index/:fileName|index/:fileName.html
  3. The Express router then processed this to create the regex 
    /^\/index\/([^\/]+?)|index\/([^\/]+?)\.html(?:\/(?=$))?$/i
  4. Due to the lack of clear grouping specifications for the pipe, it ended up behaving as a match for either /^\/index\/([^\/]+?)/i or 
    /index\/([^\/]+?)\.html(?:\/(?=$))?$/i
  5. In this case, the former pattern satisfied the expression by matching just the first character in that group, thanks to its lazy match and unnecessary requirements at the end.

To simulate the process and better understand the resulting regex, I utilized tools like Express Route Tester and https://regex101.com/r/kN5kW9/1.

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