[twic]

I was reading the description of Jsonnet and wondering why we don't just use JavaScript. Read a file, evaluate it, take the value of the last expression as the output, and blat it out as JSON.

The environment could be enriched with some handy functions for working with structures. They could just be normal JavaScript functions. For example, a version of Object.assign which understands that "key+" syntax in objects. Or a function which removes entries from arrays and objects if they have undefined values, making it easy to make entries conditional.

Those things are simple enough to write on demand that this might not even have to be a packaged tool. Just a thing you do with npm.