express-middleware-filter-data

This middleware allows to filter an object returned by res.json using a query parameter. Example:

const getFilterMiddleware = require('express-middleware-filter-data');
// "filter" will be the query parameter used for filtering
const filterMiddleware = getFilterMiddleware('filter');

// express middleware
app.get('/data', filterMiddleware, function(req, res){
  res.json({  ... lot of data ... , total: 123 });
});

The client, calling this endpoint can ask to filter the response:

http://localhost:3000/data?filter=total

and it will receive:

{ total: 123 }

Filtering expressions

The filtering expressions are very powerful. You can use multiple coma separated expressions. Like:

http://localhost:3000/data?filter=user.products // filters only the content of users.products

http://localhost:3000/data?filter=users[:10]name // first ten users names

The full syntax is explained here: https://github.com/sithmel/obj-sieve or https://github.com/sithmel/obj-path-expression-parser

Errors

If the filter is formally incorrect, it won't be used. You can provide a callback to manage the error (by default it is logged in the console).

const filterMiddleware = getFilterMiddleware('filter', (e) => ... do something with the error ...);

Using obj-sieve instance

The middleware uses obj-sieve https://github.com/sithmel/obj-sieve. You can access the sieve instance on res.locals.sieve.