[Fixed] How to force Express.js to yield parameters with special characters as they are?


I am trying to complete a simple project in the freeCodeCamp "API and Microservices" curriculum.

The project is rather simple, it requires working with Express.js, some routes are provided and others must be dynamically generated. In this case, either a string or number that can be parsed as new Date() object. e.g.:

  • 1451001600000, this is a valid UNIX time in milliseconds;
  • 2016-12-25, is valid;
  • 05%20October%202011 is valid as well.

This last one got me stuck and makes the response fail every time.
As a matter of fact, it gets accepted as valid in the Date() object. However, the resulting date is wrong because Express.js apparently parses or passes parameters rid of special characters.

Therefore, 05%20October%202011 gets logged out as 05 October 2011.

I have looked in the Express.js documentation and elsewhere on MDN, etc.
Apparently, I have found several ways to do this with the query object, but not with the params object.

I have also tried to provide middlewares that could mitigate the problem, but the issue arises from the Express API itself, and providing URL parsing middlewares would not be useful because not all requests are sent with special characters.

Does anyone know how to prevent Express.js to get rid of special characters and pass the URL parameters as they are?

Remember that the routes are casually checked by FFC server, hence it is not possible to act on the input itself.

Thank you very much.


I think you’re misunderstanding the task 🙂

Anything you type into a URL in a modern browser will be passed through encodeURIComponent. For example, if you go to https://httpbin.org/get?data=one two three, the browser will issue a request like GET /get?data=one%20two%20three HTTP/2 (note that browsers may auto-convert %20 to space for you when you inspect the request headers, in Firefox you can use the Raw switch on Headers tab).
Raw switch

The reason this is done is so that you can send text like this/is/not/a/route or this&is=not&a=param as parameters without them being parsed as paths or query parameters.

Conventiently, express will auto-decode this for you, so that you see that req.params.data = 'one two three'. There is no reason to fight this behaviour. Now, if you REALLY wanted to get your percents back, you could encode the parameter back using

const encoded = encodeURIComponent(req.params.data);
console.log(encoded); // 'one%20two%20three'

For your example, what’s probably intended is that express automatically decodes 05%20October%202011 into 05 October 2011, which you can then use like new Date(myAutomaticallyDecodedParam).

If you instead send 05%2520October%25202011 to the server, it will get decoded into 05%20October%202011. It looks like Node will get the first number as the day, the first word as the month, and the first four digits after the month as the year, which for October%202011 leads to the year 2020.

If something is still unclear, please add more context or ask away 🙂

Leave a Reply

(*) Required, Your email will not be published