I am making a map using layers stored in a PostgreSQL (PostGIS) database. I am using GeoServer to successfully load layers with Leaflet in WFS format, but I wonder how to make SQL request on it through my JavaScript code.

How can I do that ? Or more generally, how can I can simply connect to a PG database within a JS script ?

2 Answers 2


You can't send SQL directly but GeoServer allows you to apply a filter to your GetFeature request as either an OGC filter (as all WFS do) or as a CQL filter.

GeoServer then translates as much as possible of that filter to SQL to pass to PostGIS and handles the rest seamlessly for you.

  • I don't really understand your answer but I gonna have a look. From what I've read so far, process to connect to a PG database may look like this : const { Client } = require('pg') const client = new Client({ host: 'my.database-server.com', port: 5334, user: 'database-user', password: 'secretpassword!!', }) I tried but I got error at first line for require('pg').
    – RG70
    Feb 28, 2020 at 14:57
  • You shouldn't connect to PG directly, just add the filter to the WFS getFeature request
    – Ian Turton
    Feb 28, 2020 at 15:16
  • Alright, but with your method, how can you iterate through lines of a PG table ? In my case, I would need to get each property of the features in a JS loop...
    – RG70
    Feb 28, 2020 at 15:22
  • Your filter is sent to PG to restrict which features are returned no need to iterate anything
    – Ian Turton
    Feb 28, 2020 at 15:30
  • Yes but the features are returned into a map format. I would just like to get the features as a JS matrix.
    – RG70
    Feb 29, 2020 at 16:52

You can't connect to server-side database via JavaScript. You should either use Geoserver to handle your request, or use another server-side language to handle it through webservices, such as Java Spring boot, php, Node.js, etc.

For example, if you want to search an area, you can write a webservice on the server-side and call it by JavaScript, and then handle the returned data to be shown on the map as tables for example.

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