Defining ENV variables with JS at build time

[iDm1]

With Webpack I can use DefinePlugin to define ENV variable at build time with JS:

new webpack.DefinePlugin({
     BUILD_TIME: new Date().toString()
});

According to Parcel documentation it's impossible to achieve without a transformer plugin. But who knows what plugin
does this? There is "parcel-transformer-inject-env", but it does nothing without Plasmo Framework.

How such a simple task is usually done with Parcel?

[joshamaju]

If you're using the parcel API, you can pass down environment variables

[davidjb]

I'm also keen to know if this is possible dynamically at build time. As has been mentioned above, it's possible to pass env when creating an instance of Parcel (https://parceljs.org/features/parcel-api/#environment-variables), but these are set and (seemingly) unable to be changed.

In order to create a build with different environment variables this seems to require creating a new Parcel instance. In the case of a watcher running, changing an environment variable means tearing down the watcher and restarting it, a costly operation.

Is it possible to pass ENV variables (or just arbitrary data) into a build at build time, or is it otherwise possible to change a Parcel's ENV variables on the fly?