How to find a object in a nested array using recursion in JS

Question

Consider the following deeply nested array:

const array = [
    {
        id: 1,
        name: \"bla\",
        children: [
            {
                id:         


        

Answer 1

This will use recursive find by level, it'll try to find the item in array and then call itself with the children of each item in the array:

New browsers will have Array.prototype.flatten but in this case I've added the flatten function separately.

const array = [{"id":1,"name":"bla","children":[{"id":23,"name":"bla","children":[{"id":88,"name":"bla"},{"id":99,"name":"bla"}]},{"id":43,"name":"bla"},{"id":45,"name":"bla","children":[{"id":43,"name":"bla"},{"id":46,"name":"bla"}]}]},{"id":12,"name":"bla","children":[{"id":232,"name":"bla","children":[{"id":848,"name":"bla"},{"id":959,"name":"bla"}]},{"id":433,"name":"bla"},{"id":445,"name":"bla","children":[{"id":443,"name":"bla"},{"id":456,"name":"bla","children":[{"id":97,"name":"bla"},{"id":56,"name":"bla"}]}]}]},{"id":15,"name":"bla","children":[{"id":263,"name":"bla","children":[{"id":868,"name":"bla"},{"id":979,"name":"bla"}]},{"id":483,"name":"bla"},{"id":445,"name":"bla","children":[{"id":423,"name":"bla"},{"id":436,"name":"bla"}]}]}];


const flatten = (arr) =>
  arr.reduce((result, item) => result.concat(item), []);
const findBy = (findFunction, subItemsKey) => (array) =>
  //array is empty (can be when children of children of children does not exist)
  array.length === 0
    ? undefined //return undefined when array is empty
    : array.find(findFunction) || //return item if found
      findBy(findFunction, subItemsKey)(//call itself when item is not found
        flatten(
          //take children from each item and flatten it
          //([[child],[child,child]])=>[child,child,child]
          array.map((item) => item[subItemsKey] || []),
        ),
      );
const findChildrenById = (array) => (value) =>
  findBy((item) => item.id === value, 'children')(array);
const findInArray = findChildrenById(array);

console.log('found', findInArray(99));
console.log('not found', findInArray({}));