I'm searching for a way to determine in code whether it is being run with jsBrowserDevelopmentRun or jsBrowserProductionWebpack. I saw a suggestion to use multiple html pages and set variables in them, but the method to do that is not obvious.

I don't feel that we have such intrinsic in our kotlin.js package, but you can make a ticket for it, and it's possible that we would add it.

You can use webpack

DefinePlugin

for this. Put this in some *.js file in `webpack.config.d`:

;(function() {
    const webpack = require('webpack')
    config.plugins.push(new webpack.DefinePlugin({
        build_mode: JSON.stringify(config.mode),
    }));
})();

Thank you so much! That's exactly what I was looking for.

Even special plugin exists, which do configuration in Gradle