deep merge two objects

deep-merge-object.js

// mergeDeep({ a: {b: 2} }, { a: { b: 5 }})
// = { a: { b: 5 }}

function mergeDeep(obj1, obj2) {
  
  let newObj = { ...obj2 };

  const recurseObj = (obj1, obj2) => {
    Object.keys(obj1).forEach(key => {
      if (typeof obj1[key] === "object" && obj2[key] !== undefined) {
        recurseObj(obj1[key], obj2[key]);
      } else if (obj2[key] === undefined) {
        obj2[key] = obj1[key];
      }
    });
  };

  recurseObj(obj1, newObj);
  return newObj;
}