from flat nested array to tree

getNestedChildren.js

  const getNestedChildren = (flatArray, parent) => {
    const nestedResult = [];
    Object.values(flatArray).forEach((item) => {
      if (item.parentId === parent) {
        const children = getNestedChildren(flatArray, item.id);
        if (children.length) {
          /* eslint-disable-next-line no-param-reassign */
          item.children = children;
        }
        nestedResult.push(item);
      }
    });
    return nestedResult;
  };