如何将 js 对象转换为点符号字符串

var data = {
  a: {
    b: 1,
    c: {
      d: 8
    }
  },
  e: {
    f: {
      g: 9
    },
    h: 10,
    i: [1, 2, 3]
  }
};


function toDotList(obj) {
  function walk(into, obj, prefix = []) {
    Object.entries(obj).forEach(([key, val]) => {
      if (typeof val === "object" && !Array.isArray(val)) walk(into, val, [...prefix, key]);
      else into[[...prefix, key].join(".")] = val;
    });
  }
  const out = {};
  walk(out, obj);
  return out;
}

console.log(toDotList(data));