A function that takes an array of objects as input along with its children. How to get such an array with multilevel nesting?

Question

JavaScript

There is an array of objects

const obj = [
  {
    name: 'hunter',
    isExpanded: true,
    children: [
                {
                  name: 'rain',
                  isExpanded: true,
                  children: [
                    {name: 'zevs',
                     isExpanded: false
                    },
                    {name: 'jupiter',
                     isExpanded: false
                    },
                  ]
                },
                {
                  name: 'vortex',
                  isExpanded: false
                },
                {
                  name: 'fray',
                  isExpanded: false
                },
              ]      
  },
  {
    name: 'focus',
    isExpanded: false,
    children: [
                {
                  name: 'dizik',
                  isExpanded: false
                },
                {
                  name: 'shank',
                  isExpanded: true,
                  children:[
                    {name: 'storm',
                     isExpanded: false},
                  ]
                },
                {
                  name: 'free',
                  isExpanded: false
                },
              ]      
  },
  {
    name: 'devil',
    isExpanded: true,
    children: [
                {
                  name: 'defavu',
                  isExpanded: false
                },
                {
                  name: 'hope',
                  isExpanded: true,
                  children: [
                    {name: 'rilay',
                    isExpanded: false},
                    {name: 'truth',
                    isExpanded: false}
                  ]
                },
                {
                  name: 'miracle',
                  isExpanded: false
                },
              ]      
  }
]

You need to get an array with a level 0 of objects along with all child elements, provided that the parent has the expansion flag set to true. I tried to bring this case through recursion, but there was a difficulty with the transition to the previous level. I can go to the neighboring child element (in this case, I store a link to their parent), but if I return to the parent and already consider it as a child element, it doesn’t work out. [{name:hunter,isExpanded:true},{name:'rain',isExpanded:true}, {name:"rain",isExpanded:true}, {name:"zevs", isExpanded: false},{name: "jupiter",isExpanded:false},{name:"vortex",isExpanded:false},{name:"fray",isExpanded:false},{name:"focus",isExpanded:false}, {name:"devil ",isExpanded:true},{name:"defavu",isExpanded:false}, {name:"shank",

Answer 1

const flat = arr =>
  (arr || []).reduce((acc, { children, ...n }) => {
    if (n.isExpanded || !children) {
      acc.push(n, ...flat(children));
    } else {
      acc.push({ ...n, children });
    }

    return acc;
  }, []);

UPD. If nested levels need to be expanded despite isExpanded: falseone of the ancestors having a level higher than the parent, then

const flat = arr =>
  (arr || []).reduce((acc, { children, ...n }) => {
    const flatChildren = flat(children);

    if (n.isExpanded || !children) {
      acc.push(n, ...flatChildren);
    } else {
      acc.push({ ...n, children: flatChildren });
    }

    return acc;
  }, []);