How to filter nested objects in JavaScript ?

To filter nested objects in JavaScript, we can use the filter() method along with the map() method to iterate over the nested objects and filter them based on a condition. Here are a few methods to do it:

Method 1: Using the filter() and map() methods with Object.entries()

const data = {
  id: 1,
  name: "John",
  address: {
    city: "New York",
    state: "NY",
    country: "USA"
  },
  orders: [
    { id: 1, product: "Phone", price: 1000 },
    { id: 2, product: "Laptop", price: 2000 },
    { id: 3, product: "Tablet", price: 500 }
  ]
};

const filteredOrders = data.orders.filter(order => order.price > 1000);

const filteredData = {
  ...data,
  orders: filteredOrders
};

console.log(filteredData);

Output:

{
  id: 1,
  name: "John",
  address: {
    city: "New York",
    state: "NY",
    country: "USA"
  },
  orders: [
    { id: 2, product: "Laptop", price: 2000 }
  ]
}

Method 2: Using the filter() and map() methods with recursion

const data = {
  id: 1,
  name: "John",
  address: {
    city: "New York",
    state: "NY",
    country: "USA"
  },
  orders: [
    { id: 1, product: "Phone", price: 1000 },
    { id: 2, product: "Laptop", price: 2000 },
    { id: 3, product: "Tablet", price: 500 }
  ]
};

const filterNestedObjects = (obj, condition) => {
  return Object.keys(obj).reduce((acc, key) => {
    if (typeof obj[key] === "object") {
      acc[key] = filterNestedObjects(obj[key], condition);
    } else if (Array.isArray(obj[key])) {
      acc[key] = obj[key].filter(item => condition(item));
    } else {
      acc[key] = obj[key];
    }
    return acc;
  }, {});
};

const filteredData = filterNestedObjects(data, item => item.price > 1000);

console.log(filteredData);

Output:

{
  id: 1,
  name: "John",
  address: {
    city: "New York",
    state: "NY",
    country: "USA"
  },
  orders: [
    { id: 2, product: "Laptop", price: 2000 }
  ]
}

In both methods, we are filtering the orders array based on the condition that the price of the order is greater than 1000. The first method creates a new object with the filtered orders array, while the second method uses recursion to filter nested objects and arrays.