input: ["doc", "doc", "image", "doc(1)", "doc"]

output: ["doc", "doc(1)", "image", "doc(1)(1)", "doc(2)"]

The issue:

{used[name]++} this part of the code is tricking me.

I don't understand line and how I'm not assigning 1 to the first thing

the code is working the way it should from trial and error; but I'm having a hard to wrapping my brain around this loop.

my understanding:

we loop through the names, then each name that starts with docs; we assign newName to doc1

What I tried:

used[newName] = 6;

results: [doc, doc(6), image, doc(1), doc(7)]

this ended up confusing me more. it's late and I might just need some sleep.

const solution = names => {
    const used = {};
    return names.map(name => {
        let newName = name;
        while (used[newName]) {
            newName = `${name}(${used[name]++})`;
        }
        used[newName] = 1;
        return newName;
    });
};