Generate file names like a file manager

name_generator.js

const generateNameInContext = (name, defaultName, namesContext) => {
    if (!defaultName) {
        defaultName = "Item";
    }

    if (!name) {
        name = defaultName;
    }

    const fmtName = (number) => `${name}(${number})`;
    let pattern = /\((.*?)\)$/; //used to find clone number in "<Name>(idx)"

    if (namesContext.includes(name) === false) {
        return name;
    }

    let cloneNumbers = namesContext
        .map(n => [n, pattern.exec(n)])
        .filter(([_, match]) => match)
        .filter(([n, match]) => name === n.substring(0, match.index))
        .map(([_, match]) => parseInt(match[1]));

    if (cloneNumbers.length === 0) {
        return fmtName(1);
    }

    let max = Math.max(...cloneNumbers);
    return fmtName(max + 1);
}