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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??

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)

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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));

Recursion and stack, The 1st case is the base of recursion, the trivial case, when we get an array. The 2nd case when we get an object is the recursive step. Tag: javascript,recursion. I am going through Javascript from the beginning. No shortcuts, no framework, nothing. Just plain Javascript. And just for the fun of it, I am doing every exercise. Now, when I get to this one question: Write a function arrayToList that builds up a data structure like

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));

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You Might Not Need that Recursive Function in JavaScript, Edit: I have been getting quite a bit of feedback interpreting this to build a hierarchical object tree structure based on a flat array of objects. JavaScript recursive function examples. Let’s take some examples of using the recursive functions. 1) A simple JavaScript recursive function example. Suppose that you need to develop a function that counts down from a specified number to 1. For example, to count down from 10 to 1: 3 2 1. The following shows the countDown() function:

Array.prototype.flat(), const arr = [1, 2, [3, 4, [5, 6]]]; // to enable deep level flatten use recursion with depth) { if(depth === undefined) { depth = 1; } for(const item of array) { if(Array. See the Pen javascript-recursion-function-exercise-4 by w3resource (@w3resource) on CodePen. Improve this sample solution and post your code through Disqus Previous: Write a JavaScript program to get the integers in range (x, y).

Thinking about Recursion: How to Recursively Traverse JSON , In the code above, printArrayRecursive prints one element from the list, then calls I often find myself writing recursive functions to find every property of an arbitrary JSON object, Recursively print all properties of a JSON object: Benchmarking Array Traversal in Javascript - Going Backwards is Fastest. Arrays are Objects. Arrays are a special type of objects. The typeof operator in JavaScript returns "object" for arrays. But, JavaScript arrays are best described as arrays. Arrays use numbers to access its "elements". In this example, person[0] returns John:

Comments
  • 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?
  • @GerardoFurtado but the level of child is unpredictable
  • What have you tried? Where did it go wrong? Post your code here, this isn't a free code writing service. ;-)
  • @iambatman Yes, I can see that. I was just trying to make clear that "recursion" defines a function, not an array.
  • @RobG I just looped the array with recursion but stuck with idea of filtering
  • 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).
  • 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?
  • @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.
  • suppose in the matching object I want to change isParent key to true
  • Just result.isParent = true should work (where result is the object you get after you call find).