Lodash Get 实现

const a = {
  b: {
    c: [1, 2, 3],
  },
};
 
const get = (obj, path, defaultValue = undefined) => {
  if (path.length === 0) {
    return obj;
  }
  if (!obj) {
    return defaultValue;
  }
  if (typeof path === "string") {
    path = path.replace(/\[/g, ".").replace(/\]/g, "").split(".");
  }
  let p = path.shift();
  return get(obj[p], path);
};
 
const res = get(a, "b.c[3]");
 
console.log(res);