I have an array of objects that can be of any length and any depth. I need to be able to find an object by its id and then modify that object within the array. Is there an efficient way to do this with either lodash or pure js?

I thought I could create an array of indexes that led to the object but constructing the expression to access the object with these indexes seems overly complex / unnecessary

edit1; thanks for all yours replies I will try and be more specific. i am currently finding the location of the object I am trying to modify like so. parents is an array of ids for each parent the target object has. ancestors might be a better name for this array. costCenters is the array of objects that contains the object I want to modify. this function recurses and returns an array of indexes that lead to the object I want to modify

var findAncestorsIdxs = function(parents, costCenters, startingIdx, parentsIdxs) {
            var idx = startingIdx ? startingIdx : 0;
            var pidx = parentsIdxs ? parentsIdxs : [];

            _.each(costCenters, function(cc, ccIdx) {
                if(cc.id === parents[idx]) {
                    console.log(pidx);
                    idx = idx + 1;
                    pidx.push(ccIdx);
                    console.log(pidx);
                    pidx = findAncestorsIdx(parents, costCenters[ccIdx].children, idx, pidx);
                }
            });
            return pidx;
        }; 

Now with this array of indexes how do I target and modify the exact object I want? I have tried this where ancestors is the array of indexes, costCenters is the array with the object to be modified and parent is the new value to be assigned to the target object

var setParentThroughAncestors = function(ancestors, costCenters, parent) {
            var ccs = costCenters;
            var depth = ancestors.length;
            var ancestor = costCenters[ancestors[0]];
            for(i = 1; i < depth; i++) {
                ancestor = ancestor.children[ancestors[i]];
            }
            ancestor = parent;
            console.log(ccs);
            return ccs;
        };

this is obviously just returning the unmodified costCenters array so the only other way I can see to target that object is to construct the expression like myObjects[idx1].children[2].grandchildren[3].ggranchildren[4].something = newValue. is that the only way? if so what is the best way to do that?

I have an array of objects that can be of any length and any depth. I need to be able to find an object by its id and then modify that object within the array. Is there an efficient way to do this with either lodash or pure js?

I thought I could create an array of indexes that led to the object but constructing the expression to access the object with these indexes seems overly complex / unnecessary

edit1; thanks for all yours replies I will try and be more specific. i am currently finding the location of the object I am trying to modify like so. parents is an array of ids for each parent the target object has. ancestors might be a better name for this array. costCenters is the array of objects that contains the object I want to modify. this function recurses and returns an array of indexes that lead to the object I want to modify

var findAncestorsIdxs = function(parents, costCenters, startingIdx, parentsIdxs) {
            var idx = startingIdx ? startingIdx : 0;
            var pidx = parentsIdxs ? parentsIdxs : [];

            _.each(costCenters, function(cc, ccIdx) {
                if(cc.id === parents[idx]) {
                    console.log(pidx);
                    idx = idx + 1;
                    pidx.push(ccIdx);
                    console.log(pidx);
                    pidx = findAncestorsIdx(parents, costCenters[ccIdx].children, idx, pidx);
                }
            });
            return pidx;
        }; 

Now with this array of indexes how do I target and modify the exact object I want? I have tried this where ancestors is the array of indexes, costCenters is the array with the object to be modified and parent is the new value to be assigned to the target object

var setParentThroughAncestors = function(ancestors, costCenters, parent) {
            var ccs = costCenters;
            var depth = ancestors.length;
            var ancestor = costCenters[ancestors[0]];
            for(i = 1; i < depth; i++) {
                ancestor = ancestor.children[ancestors[i]];
            }
            ancestor = parent;
            console.log(ccs);
            return ccs;
        };

this is obviously just returning the unmodified costCenters array so the only other way I can see to target that object is to construct the expression like myObjects[idx1].children[2].grandchildren[3].ggranchildren[4].something = newValue. is that the only way? if so what is the best way to do that?

• javascript
• lodash

• You have to iterate recursively over all objects and compare against the ID you are looking for. – Felix Kling Commented Aug 29, 2014 at 13:28
• You say you have an array of objects. Arrays in JavaScript are indexed, not associative, so presumably you mean find an object by its index, not ID. Else, please clarify. – Mitya Commented Aug 29, 2014 at 13:28
• each object in the array has a unique id. I want to find a given object by that id and then change that object – Mark Commented Aug 29, 2014 at 13:33
• 1 See Access / process (nested) objects, arrays or JSON. It has a section about recursion. – Felix Kling Commented Aug 29, 2014 at 13:49
• 1 You're now stating the problem in a way which presupposes a particular, awkward-to-impossible solution, which is to return some kind of "index" into an object which can then be used to reference something down within the object. But there is no such animal. You are better off designing your solution so that you pass a callback which is invoked to handle the modification when the sub-object of interest is found. – user663031 Commented Aug 29, 2014 at 14:19

6 Answers 6

You can use JSON.stringify for this. It provides a callback for each visited key/value pair (at any depth), with the ability to skip or replace.

The function below returns a function which searches for objects with the specified ID and invokes the specified transform callback on them:

function scan(id, transform) {
  return function(obj) {
    return JSON.parse(JSON.stringify(obj, function(key, value) {
      if (typeof value === 'object' && value !== null && value.id === id) {
        return transform(value);
      } else {
        return value;
      }
  }));
}

If as the problem is stated, you have an array of objects, and a parallel array of ids in each object whose containing objects are to be modified, and an array of transformation functions, then it's just a matter of wrapping the above as

for (i = 0; i < objects.length; i++) {
    scan(ids[i], transforms[i])(objects[i]);
}

Due to restrictions on JSON.stringify, this approach will fail if there are circular references in the object, and omit functions, regexps, and symbol-keyed properties if you care.

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_native_JSON#The_replacer_parameter for more info.

As Felix Kling said, you can iterate recursively over all objects.

// Overly-complex array
var myArray = {
    keyOne: {},
    keyTwo: {
        myId: {a: '3'}
    }
};
var searchId = 'myId', // Your search key
    foundValue, // Populated with the searched object
    found = false; // Internal flag for iterate()

// Recursive function searching through array
function iterate(haystack) {
    if (typeof haystack !== 'object' || haystack === null) return; // type-safety
    if (typeof haystack[searchId] !== 'undefined') {
        found = true;
        foundValue = haystack[searchId];
        return;
    } else {
        for (var i in haystack) {
            // avoid circular reference infinite loop & skip inherited properties
            if (haystack===haystack[i] || !haystack.hasOwnProperty(i)) continue;

            iterate(haystack[i]);
            if (found === true) return;
        }
    }
}

// USAGE / RESULT
iterate(myArray);
console.log(foundValue); // {a: '3'}
foundValue.b = 4; // Updating foundValue also updates myArray
console.log(myArray.keyTwo.myId); // {a: '3', b: 4}

All JS object assignations are passed as reference in JS. See this for a complete tutorial on objects :)

Edit: Thanks @torazaburo for suggestions for a better code.

If each object has property with the same name that stores other nested objects, you can use: https://github.com/dominik791/obj-traverse

findAndModifyFirst() method should solve your problem. The first parameter is a root object, not array, so you should create it at first:

var rootObj = {
  name: 'rootObject',
  children: [
    {
      'name': 'child1',
       children: [ ... ]
    },
    {
       'name': 'child2',
       children: [ ... ]
    }
  ]
};

Then use findAndModifyFirst() method:

findAndModifyFirst(rootObj, 'children', { id: 1 }, replacementObject)

replacementObject is whatever object that should replace the object that has id equal to 1.

You can try it using demo app: https://dominik791.github.io/obj-traverse-demo/

Here's an example that extensively uses lodash. It enables you to transform a deeply nested value based on its key or its value.

const _ = require("lodash")
const flattenKeys = (obj, path = []) => (!_.isObject(obj) ? { [path.join('.')]: obj } : _.reduce(obj, (cum, next, key) => _.merge(cum, flattenKeys(next, [...path, key])), {}));


const registrations = [{
  key: "123",
  responses:
  {
    category: 'first',
  },
}]


function jsonTransform (json, conditionFn, modifyFn) {

  // transform { responses: { category: 'first' } } to { 'responses.category': 'first' }
  const flattenedKeys = Object.keys(flattenKeys(json));

  // Easily iterate over the flat json
  for(let i = 0; i < flattenedKeys.length; i++) {
    const key = flattenedKeys[i];
    const value = _.get(json, key)

    // Did the condition match the one we passed?
    if(conditionFn(key, value)) {

      // Replace the value to the new one    
      _.set(json, key, modifyFn(key, value)) 
    }
  }

  return json
}

// Let's transform all 'first' values to 'FIRST'
const modifiedCategory = jsonTransform(registrations, (key, value) => value === "first", (key, value) => value = value.toUpperCase())

console.log('modifiedCategory --', modifiedCategory)
// Outputs: modifiedCategory -- [ { key: '123', responses: { category: 'FIRST' } } ]

I needed to modify deeply nested objects too, and found no acceptable tool for that purpose. Then I've made this and pushed it to npm.

https://www.npmjs.com/package/find-and

This small [TypeScript-friendly] lib can help with modifying nested objects in a lodash manner. E.g.,

var findAnd = require("find-and");

const data = {
  name: 'One',
  description: 'Description',
  children: [
    {
      id: 1,
      name: 'Two',
    },
    {
      id: 2,
      name: 'Three',
    },
  ],
};

findAnd.changeProps(data, { id: 2 }, { name: 'Foo' });

outputs

{
  name: 'One',
  description: 'Description',
  children: [
    {
      id: 1,
      name: 'Two',
    },
    {
      id: 2,
      name: 'Foo',
    },
  ],
}

https://runkit.com/embed/bn2hpyfex60e

Hope this could help someone else.

I wrote this code recently to do exactly this, as my backend is rails and wants keys like:

first_name

and my front end is react, so keys are like:

firstName

And these keys are almost always deeply nested:

user: {
  firstName: "Bob",
  lastName: "Smith",
  email: "[email protected]"
}

Becomes:

user: {
  first_name: "Bob",
  last_name: "Smith",
  email: "[email protected]"
}

Here is the code

function snakeCase(camelCase) {
  return camelCase.replace(/([A-Z])/g, "_$1").toLowerCase()
}

export function snakeCasedObj(obj) {
  return Object.keys(obj).reduce(
    (acc, key) => ({
      ...acc,
      [snakeCase(key)]: typeof obj[key] === "object" ? snakeCasedObj(obj[key]) : obj[key],
    }), {},
  );
}

Feel free to change the transform to whatever makes sense for you!