The Quest Begins (The "Why")

I still remember the first time I opened a legacy codebase and felt like I’d stepped into a dark dungeon without a torch. The file was a single 800‑line function called processData. Inside, variables bore names like tmp, x, flag, and comments that tried to explain every line:

// TODO: refactor this mess

function processData(input) {

let r = []; // result array