The Realm JavaScript SDK has limited support for running behind an HTTP proxy:

Current limitations:

• This is currently only supported on Realm JS v10.3.0 or higher running on Node.js.
• You must install the fetch-with-proxy package manually.
• You must set the HTTPS_PROXY environment variable, hence the proxy cannot be set at runtime or on a per-app basis.
• HTTPS connections from the client to the proxy server, is not supported. I.e. the URL specified in the HTTPS_PROXY must start with http://.

Installing fetch-with-proxy

In the time of writing this tutorial a manual step is required to switch out the node-fetch package used by the network transport layer. NPM CLI v6.9.0 or higher is required.

After installing Realm JS, run the following command to install a different package into our Network Transport package:

npm install node-fetch@npm:fetch-with-proxy --prefix node_modules/realm-network-transport

Setting HTTPS_PROXY and running a script

Let's say you have a index.js script that you want to run, while routing all of Realm JS's requests through an HTTP proxy located at http://127.0.0.1:3128.

On a Unix system you can simply prefix the assignment of an environment variable before the command, like this:

HTTPS_PROXY=http://127.0.0.1:3128 node index.js

On a Windows system you have to configure the variable through "Advanced system settings" > "Environment Variables" > "Edit System Variable".