Which of the presets does Babel use when compiling code?

Question

JavaScript

In my .babelrc file I have:

"presets": [
        "es2015",
        "stage-0"
    ],

How does compilation work in this case? If the first preset does not know what this code is, then the next one comes into play, or what?

Answer 1

Each preset is just a set of plugins
plugins are of 2 types - syntactic and transformational
syntactic plugins work at the stage of parsing the code and are needed to build an ast tree
transformation plugins work with a ready ast tree and change it
all plugins of the same type work essentially together