deepclone.js

function deepCopy(source) {
    return deepCopyHelper(source, {});
}

function deepCopyHelper(source, target) {
    for(let key in source) {
        const value = source[key];
        if(typeof value !== "object") {
            target[key] = value;
        } else {
            target[key] = Array.isArray(value) ? [] : {};
            deepCopyHelper(source[key], target[key]);
        }
    }

    return target;
}

// Input:
const c = {
    n: [1, 2, 3],
    l: ['a', 'b', 'c'],
    o: { prop: 1 },
    b: true,
    x: 1,
};

console.log(deepCopy(c));