Merge two array of objects based on a key javascript Apr 27, 2023 · If the key already exists in the clone, and both the current item at that key and the new value are of the same type, and the value is an array or object, we want to recursively merge them together. map() method to iterate over the array of keys. Jan 24, 2017 · * Merges two arrays of objects (`arrayA` and `arrayB`) into one, resolving conflicts based on a key returned by the `callbackFn`. It allows the privilege to obtain a list of parameters from an array. Jun 8, 2025 · Combining data from multiple sources is a common task in real-world projects. The resulting array, joinedArray, should contain all the unique objects from both arrays, sorted in ascending order of their id values. I have two different variable g and c. arrayList2 values will be overwrite the arrayList1. Jul 9, 2021 · I'm trying to merge two objects which, both have same similar key, but different values. values() iterator of the Map converted to an array. In this demo, the arrays a and b are first converted into objects (where userId is the key), then merged, and the result converted back to an array (_. assign called on it and the current record. Nov 20, 2020 · We are required to write a JavaScript function that takes in one such object. Mar 26, 2024 · Combine 2 JavaScript object arrays based on a key Have you ever needed to combine two arrays of objects? Maybe each one contains partial information about the same objects, and you want to merge them into a single array. Jul 24, 2023 · Now we need to merge the two array of objects into a single array by using id property because id is the same in both array objects. assign(). flatten is then necessary because _. keys method and checking which object from arr2 has maximum matching object with the item of arr1. And our function should merge the child array objects into corresponding parent objects. Note: Both arrays should be the same length to get a correct answer. That function will use the reduce() method to produce an object of key/value pair. Just I am trying to merge those two arrays into one array object. g. First concatenate the two arrays into a single array, then detect and combine objects with matching id's. In order to do so, we can use Object. forEach () method calls the provided function once for Jul 23, 2025 · In this approach, Combines values of two maps by converting entries to arrays, concatenating them, then using reduce to update or set values based on matching keys. It sounds relatively straightforward at first, but there's more to the story that prevented me using the spread operator or Object. ) Mar 20, 2024 · You may, for example, want to merge arrays or objects, or overwrite values for certain keys. For example, if you have a list of user objects and you want to combine them into a single object based on a unique property, Lodash provides useful functions to simplify this process. Oct 4, 2016 · I am trying to combine two array objects with different array objects based on flight key. keys() to get the keys of both objects, create a Set from them, and use the spread operator () to create an array of all the unique keys. id && item) We spread the properties of each into a new object and return it. Aug 27, 2020 · I have two arrays videos and storeProducts. Have a look at the following You can create an object keyed by ID and push elements with the same ID to them, then convert back to an array. Let’s make this task simple and elegant! Not a Member? Read for FREE here. id using Object. Jan 21, 2021 · This is a continuation of solution described in Combine json arrays by key, javascript, except that the input JSON has deeper level of nested array objects: json1 [ { "id": 1, & Aug 31, 2021 · In this post we will cover everything about how to merge two objects in JavaScript including, deep, and shallow merges, as well as same keys and preventing overwriting keys. Each element in the first array becomes a property name in the object, and the corresponding element in the second array becomes its value. Conclusion To merge two array of objects based on a key with JavaScript, we can use the array map and find methods and the spread operator. Feb 23, 2021 · For each item of arr1 we are finding the keys using Object. But merging arrays of objects by a unique key? That’s where many developers get stuck (or write way too much code). values adds an extra level of array. (The last question verbally asks for an inner join, but by the description and the output example it is actually a question asking for a full outer join. This is how the function will look like: Sep 9, 2023 · In JavaScript, merging objects is a fundamental operation that allows developers to combine the properties and values of multiple objects into a single, cohesive entity. Oct 14, 2025 · In JavaScript, an object can be created by combining two arrays: one for keys and one for values. I Got the expected output but I am worying to do with efficient and performance way. This is more efficient than looping through on every iteration for larger arrays: Feb 9, 2022 · @Shatsuki That question is about merging arrays of strings, this question is about merging an array of objects, where some of the objects themselves might need to be merged. response = [ In this article, we would like to show you how to merge objects in an array with the same keys in JavaScript. The lodash's union methods create an array of unique values. Nov 4, 2025 · Merging two arrays of objects based on a common key is a frequent task in JavaScript, especially when combining data from multiple sources (e. To solve the problem, in the example below we use the following methods: forEach() - to iterate over all objects inside array, filter() - to check if an object with a given type property value already exists, concat() - if an object with a given type already exists, the current object Feb 15, 2024 · Merging nested objects in JavaScript is a common task in web development, and it’s crucial to handle it correctly to avoid unexpected behavior. I tried to find materials online but ended up only on merging 2 array of objects. Whether you’re working with configurations, API Jun 2, 2022 · Use _. This tutorial provides a comprehensive explanation of the merging process, including handling cases where objects share the same 'id'. But I have multiple array of objects in an array. Aug 23, 2024 · Merging multiple arrays of objects by a shared key, like ID, in JavaScript, is used when consolidating data from various sources, such as API responses or databases. For each item with the same ids we combine the selected arrays. The result is the . union to do this, but it simply overwrites the values from the second array into the first one Mar 10, 2016 · Nor among the answers to the questions Merge two array of objects based on a key or How can I perform an inner join with two object arrays in JavaScript?. Use the Object. * For objects with the same key, properties from the objects in the second array (`arrayB`) overwrite those in the first (`arrayA`). videos array may have product_id and storeProducts must have product_id. Apr 3, 2015 · Merge two arrays of objects based on key in javascript Asked 10 years, 2 months ago Modified 10 years, 2 months ago Viewed 888 times How to merge two arrays based on a key? To merge the two arrays on id, assuming the arrays are equal length: Each list gets reduced to a single object where the keys are ids and the values are the objects. Oct 18, 2009 · var array3 = ["Vijendra","Singh","Shakya"]; The output array should have repeated words removed. The following terms I used. Then we merge the two item together. I need merge these based on both produt_id same else only push video items in array. Adjust the key and the object properties according to your specific use case. The resulting array, mergedArray, contains unique objects from both arrays. This process involves combining objects that have the same key into a single object, allowing developers to manage and manipulate complex datasets more effectively. We choose to use an object internally here to for faster lookup of existing dates, you could reduce We need to merge two arrays, arr1 and arr2, based on their "id" key. values) (getting rid of the keys). Nov 22, 2015 · What is the best way to merge array contents from JavaScript objects sharing a key in common? How can array in the example below be reorganized into output? Here, all value keys (whether an array o Apr 25, 2019 · Hello everyone, in this article, I want to explain how to merge two array object based on key values. Oct 3, 2021 · Level up your programming skills with exercises across 52 languages, and insightful discussion with our dedicated team of welcoming mentors. This allows dynamic construction of objects from array data. _. terms: All values need to merge. Return an object containing the current key-value pair on each iteration. Jan 23, 2019 · 5 I have two array object (arrayList1,arrayList2). Using the spread operator or the concat () method is the most optimal solution. If there’s a value at the given key already, it gets object. The function should merge part1 and part2 of the object to form an array of objects like this − Jun 8, 2023 · Solution We're going to create a function that takes in two arguments: one for the array of keys, and the other for the values. reduce() to combine the two arrays into one. Oct 14, 2025 · Array : How to Merge two array of objects based on same key and value in javascript? To Access My Live Chat Page, On Google, Search for "hows tech developer connect" As promised, I have a hidden Aug 24, 2016 · @Andreas Little follow-up question: How can I achieve the same result, but when the objects in the array contain another object as value? So for example: [ { label: 'private', value: {propa: 'some text', propb: 12}} ] I want the result to merge, so that if the label is the same the properties from the original value get merged with the Dec 7, 2015 · I suggest you transform array 2 into an object so that you can find things in it easily, and then use that to map array 1 into the result you want. It is mostly used in the variable array where there is more than 1 value is expected. Javascript objects are key-value paired Oct 15, 2021 · There are more than a couple of ways to merge two or more arrays into one in JavaScript. This is how JavaScript objects area really merged: Only keys in the to object which are not objects themselves will be overwritten by from. Using concat () Method and Set () Object The concat () method is used to merge two arrays and then use the Set () object to remove the duplicate items from the merged array. Jul 21, 2022 · You can use Array. So how would you go about doing that? May 11, 2022 · We find the object with the same id value as the one being looped through in a1 with a2. If the value is matched in a2, I want to merge it with a1 and create new array. id === itm. Oct 13, 2020 · I need to merge a list of array of objects by a key. # Create an Object from Two Arrays using Object. Jan 11, 2019 · In other words, we use the IDs as the keys of an object, this will give you O(1) on access the data, and O(1) in the exists test. ,Here is a way where you first build an index keyed by id (sparse array) to detect and combine objects with matching id values, which then finally are concatenated back into a normal array Mar 7, 2024 · Learn how to merge two arrays of objects based on a common 'id' key in JavaScript. A useful guide for web developers with code examples. Feb 4, 2023 · Learn how to merge objects in JavaScript with different methods and examples. Typically, this involves aligning objects by a shared property (like `id`, `email`, or `name`) and combining their properties into a single object. I tried to use _. The filter () method is applied to array2, ensuring that only objects not present in array1 (based on the id property) are included. I was using the underscore solution from here merge two json object based on key value in javascript, but it turns out it doesnt Lodash has a merge method that works on objects (objects with the same key are merged). Dec 21, 2017 · I need to merge JSON objects with same key into one so that it gets an object or array (doesn't matter if result is an object or array) which holds the key and an array for the values example JSON May 7, 2015 · I need to merge two json object based on key value using javascript. , merging user profiles with their contact details). When two keys are the same, the generated object will have a value for the rightmost key. How do I merge two arrays in JavaScript so that I get only the unique items from each array in the same order they were inserted into the original arrays? Where the two arrays are being joined based on the 'id' field and extra data is simply being added. Dec 18, 2014 · 96 This question already has answers here: How to convert an array of objects to object with key value pairs (7 answers) How to concatenate properties from multiple JavaScript objects (14 answers) Jul 23, 2025 · 2. I want them to keep the different keys and but place them together in the matching key value here my first o We have to write a function that converts this array into an array where all the headings (h1, h2, h3 …) that have the same id get clubbed inside the same object. Finally filter out all null values. Mar 22, 2021 · Here is an option using a Map, iterating the input using a forof loop and merging objects with the same post. Everything else will be really merged. [Approach -1 ] Using for-each loop The arr. May 11, 2022 · We find the object with the same id value as the one being looped through in a1 with a2. Jun 6, 2022 · Introduction At work recently, I encountered an interesting problem: I needed to merge multiple JavaScript objects together in an array based on their matching keys. js: merge two arrays of keys and values to an object using underscore. var g = [ { id: 36, name: 'AAA', goal: 'yes' }, The same question with underscore. Jun 4, 2019 · I have referred questions listed below, but got not related answer. For example, I want to merge each of the objects in the arrays if they have the same values for 'fruit' k Nov 23, 2020 · We are required to write a JavaScript function that takes in these two arrays. Using Spread Operator The Spread operator allows an iterable to expand in places where 0+ arguments are expected. Mar 4, 2024 · The function takes 2 arrays as parameters and creates an object from the two arrays. Apr 3, 2021 · I have two arrays of objects and want to combine the two based on specific key-value pairs. JavaScript Arrays Merge two array as key value pair Fastest Entity Framework Extensions Bulk Insert Bulk Delete Aug 5, 2025 · Lodash _. Nov 11, 2022 · Answer by Kash Wade Result 1: using reduce and matching id's. . This process is crucial for managing data and creating more complex data structures, enabling the composition of objects with different attributes and functionalities. values () to turn it's values into an array. find((item) => item. Apr 10, 2018 · I am trying to merge data from json that comes in array of objects. You can get this structure using the next approach with reduce (): Aug 18, 2021 · I have the following two arrays of objects that I want to merge in one array but based on some nested keys and values inside the nested object of the first array. assign() to combine these objects. At the end, result will be an object and we can use Object. merge () method is used to merge two or more objects, starting from the left-most to the right-most to create a parent mapping object. We start by concatenating and then grouping by id. Improve your JavaScript skills now! Jan 19, 2017 · The approach here is to add items using their date property as a key to a "map" object that starts out initialized as an empty object, then summing in the clicks properties you care about. Aug 5, 2025 · The concat () method is used to merge array1 and the filtered values from array2 to create a new array. assign () This is a three-step process: Use the Array. Both array merged into one array based on key-name is type. Jul 23, 2025 · Merging an array of objects by property using Lodash is a common operation when you need to consolidate data that share a common identifier. 1. unionBy() to combine two arrays, and remove duplicates that have the same unique field (id in this case). How can I merge properties of two JavaScript objects dynamically? merge two json object based on key value in javascript Merge two Make sure that the key you are using to merge the arrays (id in this case) is common between the objects in both arrays and has unique values. Jul 11, 2025 · Here are two different ways to merge properties of two objects in JavaScript. assign() method to merge the objects. bejmka gsuh tvkr vccuq ojmv scnv zkpz jbbimlpp dujq thji pboh tocfl dnylp plob qxmvh