Creating custom JavaScript syntax with Babel

Before we proceed, if you are unfamiliar with parsers and Abstract Syntax Tree (AST), I highly recommend to checkout Vaidehi Joshi's Leveling Up One's Parsing Game With ASTs. To summarise, this is what happened when babel is parsing your code: The first step is called tokenization, where babel scans through each character and creates tokens, like function, @@, foo, (, a, ...