如何自定义express.js url查询参数解析

Question

So, req.query returns the hash of the query parameters. Even better, if a parameter is actually a json object, then it parses it into the respective json, which is awesome.

However, how can I customize this parsing? For instance, I would like a certain value to be parsed as a number, rather than as a string. Surely, I can do it post factum and modify the returned object. But, I am interesting to know whether the process can be customized in general.

EDIT

For example, consider the following request:

GET http://localhost:8000/admin/api/inventory?rowsPerPage=25&page=0&q%5Bqty%5D%5B%24lt%5D=100 

Decoding it we get:

GET http://localhost:8000/admin/api/inventory?rowsPerPage=25&page=0&q[qty][$lt]=100

Now, express converts these query parameters to

req.query = {rowsPerPage: "25", page: "0", q: {qty: {$lt: "100"}}

My problem is with "25", "0" and "100" - I want them to be numbers. So, I can either change the req.query post factum or interfere with the parsing process. I want to learn the latter.

Answer 1

the query string is parsed here connect-query.js which is based on tj's querystring parser node-querystring you may want to look into that or into nodes querystring parser. AFAIK u cannot change the qs parsing without forking express and changing something in there. anyways handling this cases in a middleware or later on in your app where you need the strings to be numbers would be better performance wise instead of checking for numbers in every request.

Answer 2

You should have a look at the req.query middleware provided by connect . It is based on node-querystring .

Answer 3

This is how I do it (using CoffeeScript and Lodash):

app.use (req, res, next) ->
  # Ensure all integer parameters are parsed correctly.
  _.each req.query, (value, key) ->
    unless isNaN value
      req.query[key] = _.parseInt value
  next()

The same can easily be achieved with JavaScript and no extensions.