recursion: get object from array javascript

Question

I have a recursive array like this

var data ={
      "isRoot": true,
      "isParent": true,
      "name": "first",
      "id": 1,
      "child": [
        {
          "isRoot": false,
          "id": 2,
          "isParent": false,
          "name": "second",
          "child": [
            {
              "id": 4,
              "child": [],
              "name": "inner",
              "isParent": false,
              "isRoot": false
            }
          ]
        },
        {
          "isRoot": false,
          "id": 3,
          "isParent": true,
          "name": "third",
          "child": []
        }
      ]
    }

child is nested it may have in any deeper level i want to get the single object from the array that matches an id.

For eg if id=4 it should return this object

    {
      "id": 4,
      "child": [],
      "name": "inner",
      "isParent": false,
      "isRoot": false
    }

How can I do that here what I found from the another post

function flatten(data) {

    data.forEach(function (element){
        //how can i do the comparison here
        if(element.child.length) {
            flatten(element.child);
        } else {

        }
    });
}

flatten(data.child);

But I couldn't get an idea of matching logic does anyone have a solution for this??

I believe that there is no such thing as recursive array. Also, you have an object... therefore, an object with several levels might be a better description, do you agree? — Gerardo Furtado
– Gerardo Furtado, Commented Feb 8, 2019 at 6:03
What have you tried? Where did it go wrong? Post your code here, this isn't a free code writing service. ;-) — RobG
– RobG, Commented Feb 8, 2019 at 6:07
@iambatman Yes, I can see that. I was just trying to make clear that "recursion" defines a function, not an array. — Gerardo Furtado
– Gerardo Furtado, Commented Feb 8, 2019 at 6:07
@RobG I just looped the array with recursion but stuck with idea of filtering — shamon shamsudeen
– shamon shamsudeen, Commented Feb 8, 2019 at 6:08

slider · Accepted Answer · 2019-02-08 17:45:16Z

1

You can do a recursive depth first search:

function find(arr, id) {
  for (var e of arr) {
    if (e.id === id) return e;
    var found = find(e.child, id);
    if (found) return found;
  }
}

var data = {
  "isRoot": true,
  "isParent": true,
  "name": "first",
  "id": 1,
  "child": [{
      "isRoot": false,
      "id": 2,
      "isParent": false,
      "name": "second",
      "child": [{
        "id": 4,
        "child": [],
        "name": "inner",
        "isParent": false,
        "isRoot": false
      }]
    },
    {
      "isRoot": false,
      "id": 3,
      "isParent": true,
      "name": "third",
      "child": []
    }
  ]
};

var result = find([data], 4);
console.log(result)

Note that I'm passing the top level data object in an array for consistency.

edited Feb 8, 2019 at 17:45

answered Feb 8, 2019 at 6:08

slider

13.1k1 gold badge29 silver badges45 bronze badges

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

5 Comments

RobG Over a year ago

The function body can be reduced to essentially a single line: for (var e of arr) return e.id === id? e : find(e.child, id).

shamon shamsudeen Over a year ago

Its worked one more question suppose I want to modify(like add another key) the matching object in the parent array ,do i need to get the index and loop again?

slider Over a year ago

@iambatman I'm not sure what you mean. Once you have a reference to the object you want using this approach, you can modify it as you like.

shamon shamsudeen Over a year ago

suppose in the matching object I want to change isParent key to true

slider Over a year ago

Just result.isParent = true should work (where result is the object you get after you call find).

Maheer Ali · Accepted Answer · 2019-02-08 06:21:31Z

You can do this with recursion.You you check if the object have child you need to loop through the child array and find the obj with id. Here is my code

var data ={
      "isRoot": true,
      "isParent": true,
      "name": "first",
      "id": 1,
      "child": [
        {
          "isRoot": false,
          "id": 2,
          "isParent": false,
          "name": "second",
          "child": [
            {
              "id": 4,
              "child": [],
              "name": "inner",
              "isParent": false,
              "isRoot": false
            }
          ]
        },
        {
          "isRoot": false,
          "id": 3,
          "isParent": true,
          "name": "third",
          "child": []
        }
      ]
    }

function find(id,obj){
	if(obj.id === id) return obj;
        //if the object has child
	if(obj.child){
                //iterating through child array
		for(let child of obj.child){
                        //call the find function again on eact child
			let childWithId = find(id,child)
                        //if there is some object in child with id
			if(childWithId){
				return childWithId;
			}
		}
	}
}
console.log(find(3,data));
console.log(find(4,data));
console.log(find(1,data));
console.log(find(2,data));

behzad besharati · Accepted Answer · 2019-02-08 06:29:25Z

The completed code, It can also find multiple matches:

var data ={
      "isRoot": true,
      "isParent": true,
      "name": "first",
      "id": 1,
      "child": [
        {
          "isRoot": false,
          "id": 2,
          "isParent": false,
          "name": "second",
          "child": [
            {
              "id": 4,
              "child": [],
              "name": "inner",
              "isParent": false,
              "isRoot": false
            }
          ]
        },
        {
          "isRoot": false,
          "id": 3,
          "isParent": true,
          "name": "third",
          "child": []
        }
      ]
    }

function search(data,id) {

    var founds=[];
    data.forEach(function (element){
      
      if(element.id===id)
        founds.push(element);
      
        if(element.child.length) {
            founds=founds.concat(search(element.child,id));
        }
    });
    return founds;
}

console.log(search([data],3));

Collectives™ on Stack Overflow

recursion: get object from array javascript

3 Answers 3

5 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

5 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related