javascript find by value deep in a nested object/array

Question

hello , I have a problem returning an object in my function, Let's say I have an object:

var elements = [{
    "fields": null,
    "id_base": "nv_container",
    "icon": "layout",
    "name": "container",
    "is_container": true,
    "elements" : [
        //another elements set here
    ]
}, 
{
    "id_base": "novo_example_elementsec",
    "name": "hello",
    "icon": "edit",
    "view": {}
}];

what i want is a function (in pure javascript) that can find an object with a specific key and value , and i have created a function but its just not working fine ? , my function :

function findNested(obj, key, value) {
    //Early return
    if (obj[key] === value) {
        console.log( 'before return' ); //until here . its fine
        return obj; //not working
    } else {
        for (var i = 0, len = Object.keys(obj).length; i <= len; i++) {
            if (typeof obj[i] == 'object') {
                this.findNested(obj[i] , key, value);
            }
        }
    }
}

I just can't see what I've done wrong ?

thanks.

user94559 · Accepted Answer · 2017-07-26 20:07:04Z

15

You're missing a return after making the recursive call. If the object is found after recursing, you need to continue to bubble that result up (by returning it). You should also be using i < len (not i <= len) as pointed out by @scott-marcus.

var elements = [{
    "fields": null,
    "id_base": "nv_container",
    "icon": "layout",
    "name": "container",
    "is_container": true,
    "elements": [
      //another elements set here
    ]
  },
  {
    "id_base": "novo_example_elementsec",
    "name": "hello",
    "icon": "edit",
    "view": {}
  }
];

function findNested(obj, key, value) {
  // Base case
  if (obj[key] === value) {
    return obj;
  } else {
    for (var i = 0, len = Object.keys(obj).length; i < len; i++) {
      if (typeof obj[i] == 'object') {
        var found = this.findNested(obj[i], key, value);
        if (found) {
          // If the object was found in the recursive call, bubble it up.
          return found;
        }
      }
    }
  }
}

console.log(findNested(elements, "icon", "layout")); // returns object
console.log(findNested(elements, "icon", "edit")); // returns object
console.log(findNested(elements, "foo", "bar")); // returns undefined

answered Jul 26, 2017 at 20:07

user94559

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1 Comment

Omar Badran Over a year ago

thanks a lot @smarx, this is what i wanted , I was looking for a solution for 6 hours , Thanks again

sergej · Accepted Answer · 2021-10-25 13:09:36Z

Just for future readers. Additionally to @user94559 answer.

A more generic way would be to iterate over the keys instead of the indices, otherwise not all nested properties will be found.
And check obj[k] before making the recursion call to ignore null values

var elements = [{
    "fields": null,
    "id_base": "nv_container",
    "icon": "layout",
    "name": "container",
    "is_container": true,
    "elements": [
      {"icon": "nested"}
    ]
  },
  {
    "id_base": "novo_example_elementsec",
    "name": "hello",
    "icon": "edit",
    "view": {}
  }
];

function findNested(obj, key, value) {

  // Base case
  if (obj[key] === value) {
    return obj;
  } else {
    var keys = Object.keys(obj); // add this line to iterate over the keys

    for (var i = 0, len = keys.length; i < len; i++) {
      var k = keys[i]; // use this key for iteration, instead of index "i"

      // add "obj[k] &&" to ignore null values
      if (obj[k] && typeof obj[k] == 'object') {
        var found = findNested(obj[k], key, value);
        if (found) {
          // If the object was found in the recursive call, bubble it up.
          return found;
        }
      }
    }
  }
}

console.log(findNested(elements, "icon", "layout")); // returns object
console.log(findNested(elements, "icon", "edit")); // returns object
console.log(findNested(elements, "foo", "bar")); // returns undefined

// this will work now
console.log(findNested(elements, "icon", "nested")); // returns object

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