join arrays of object and create new array

Question

I have an array of object like this:

 example = [
  {
    id: 1,
    child: [
      {
        id: 1,
        name: "child 1",
      },
    ],
  },
  {
    id: 2,
    child: [
      {
        id: 2,
        name: "child 2",
      },
      {
        id: 3,
        name: "child 3",
      },
    ],
  },
];

and I want to get an array of child objects like this:

[{...},{...},{...}]

I tired to loop through with map but I'm getting an array of two object.

Answer 1

You can map the child arrays to a new array and flatten them.

Array.prototype.flatMap

The flatMap() method returns a new array formed by applying a given callback function to each element of the array, and then flattening the result by one level. It is identical to a map() followed by a flat() of depth 1, but slightly more efficient than calling those two methods separately.

example = [
  {
    id: 1,
    child: [
      {
        id: 1,
        name: "child 1",
      },
    ],
  },
  {
    id: 2,
    child: [
      {
        id: 2,
        name: "child 2",
      },
      {
        id: 3,
        name: "child 3",
      },
    ],
  },
];

const newArray = example.flatMap(({ child }) => child);

console.log(newArray);