javascript tree add new property to objects at specific level

Question

I have array of objects as tree,I need to add new property named "dateType" to the 3rd level

   let tree = [
        {
          id: 1,
          name: "parent1",
          children: [
            {
              id: 2,
              name: "child1",
              children: [
                { id: 4, name: "subChild1" },
                { id: 5, name: "subChild2" }
              ]
            },
            { id: 3, name: "child2" }
          ]
        }
      ];

it should be like this:

let tree = [
    {
      id: 1,
      name: "parent1",
      children: [
        {
          id: 2,
          name: "child1",
          children: [
            { id: 4, name: "subChild1",dateType:"test" },
            { id: 5, name: "subChild2", dateType:"test" }
          ]
        },
        { id: 3, name: "child2" }
      ]
    }
  ];

how can I do that in easy way as my way it something like this:

 custTree(res) {
      let result = [];
      res.forEach(level1 => {
        level1.children.forEach(level2 => {
          level2.children.forEach(level3 => {
console.log(level3)//nothing here
            //code here
          });
        });
      });
      return result;
    },

Note:the tree is dynamic and it is from 3 levels ,but alwayes I need to update the last level

Why is tree an array? What happens if it has two or more elements -- which one will be the root of the tree? — trincot
– trincot, Commented Dec 10, 2020 at 18:52
Could you leave some feed-back? You seem to have disappeared in silence... — trincot
– trincot, Commented Dec 11, 2020 at 20:36

Nina Scholz · Accepted Answer · 2020-12-10 13:15:47Z

1

You could take an iterative and recursive approach and check if the level is zero for update with a new property.

This approach takes an zero based level for updating the objects.

function update(array, level, object) {
    if (level) array.forEach(o => update(o.children || [], level - 1, object))
    else array.forEach(o => Object.assign(o, object));
}

let tree = [{ id: 1, name: "parent1", children: [{ id: 2, name: "child1", children: [{ id: 4, name: "subChild1" }, { id: 5, name: "subChild2" }] }, { id: 3, name: "child2" }] }];

update(tree, 2, { dateType: 'test' });

console.log(tree);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Dec 10, 2020 at 13:15

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

trincot · Accepted Answer · 2020-12-10 19:11:11Z

If I understand correctly, you want to add the property at the deepest level in your tree, without knowing beforehand what the height of your tree is. So if the height of your tree is 5, you want to add the property to all nodes that are at level 5.

You could use a breadth-first traversal for this. That way you get all nodes at one particular level, each time going one level deeper. Stop when the next level turns out to be empty: it means we arrived at the deepest level.

This can be a utility function: it would return the nodes of the deepest level in an array. From there on it is easy to do with that node array whatever you want:

function getDeepestLevel(tree) {
    // Perform a breadth-first traversal
    let lastLevel = [];
    while (tree.length) {
        lastLevel = tree; // Keep track of the level that is not empty
        tree = tree.flatMap(node => node.children || []); // Next level
    }
    return lastLevel;
}

// Example tree
let tree = [{id: 1,name: "parent1",children: [{id: 2,name: "child1",children: [{ id: 4, name: "subChild1" },{ id: 5, name: "subChild2" }]},{ id: 3, name: "child2" }]}];

let level = getDeepestLevel(tree);
// Do what you want with those nodes:
for (node of level) node.dataType = "test";
console.log(tree);

Collectives™ on Stack Overflow

javascript tree add new property to objects at specific level

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related