Lodash merge arrays without duplicates

Posted by: admin November 3, Leave a comment. 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? Since many people are annoyed about prototype augmentation of Array. For those who are fortunate enough to work with browsers where ES5 is available, you can use Object.

As suggested by Dmitry see the second comment below a more performance wise solution would be to filter out the unique items in b before concatenating with a.

But if you use Babelyou can have it now. Here is a slightly different take on the loop. With some of the optimizations in the latest version of Chrome, it is the fastest method for resolving the union of the two arrays Chrome The top answer here with the double loop on every value i-1 is still significantly slower.

Those are by far the fastest of all results after going through almost all of the viable answers. This is a method I use a lot, it uses an object as a hashlookup table to do the duplicate checking.

Assuming that the hash is O 1then this runs in O n where n is a. I honestly have no idea how the browser does the hash, but it performs well on many thousands of data points. Implementation of indexOf method for other browsers is taken from MDC. If you want without duplicate you can try a better solution from here — Shouting Code.

New solution which uses Array. The easiest way to do this is either to use concat to merge the arrays and then use filter to remove the duplicates, or to use concat and then put the merged array inside a Set.

Following the functional approach a union of two Array s is just the composition of concat and filter. In order to provide optimal performance we resort to the native Set data type, which is optimized for property lookups. Anyway, the key question in conjunction with a union function is how to treat duplicates.

The following permutations are possible:. The first two permutations are easy to handle with a single function.

Since switching to plain old Object property lookups would entail a serious performance hit the following implementation just ignores the third and fourth permutation.

You would have to build a separate version of union to support them. It turns out unionn is just foldl aka Array.

Leveraging dictionaries and Jquery you could merge the two arrays and not get duplicates. Here is about the most effective one, in terms of computation time. Also it keeps the initial order of elements. Here is slightly improved faster version of it, with a downside, that arrays must not miss values:. Tags: arraysjavajavascript. February 20, Javascript Leave a comment. I keep getting th Add menu.

lodash merge arrays without duplicates

How to merge two arrays in JavaScript and de-duplicate items Posted by: admin November 3, Leave a comment.If array can't be split evenly, the final chunk will be the remaining elements. Since 3. The values falsenull0""undefinedand NaN are falsey. Since 0. Returns Array : Returns the new array of filtered values.

Since 4. Returns Array : Returns the new concatenated array. The order and references of result values are determined by the first array. Array : The values to exclude. The iteratee is invoked with one argument: value. The comparator is invoked with two arguments: arrVal, othVal. Returns Array : Returns the slice of array.

Elements are dropped until predicate returns falsey. The predicate is invoked with three arguments: value, index, array.

Note: This method mutates array. Returns Array : Returns array. Since 1. Returns number : Returns the index of the found element, else Since 2. Returns Array : Returns the new flattened array. Returns Object : Returns the new object.

Combining Arrays Without Duplicates

If fromIndex is negative, it's used as the offset from the end of array. Returns number : Returns the index of the matched value, else Array : The arrays to inspect. Returns Array : Returns the new array of intersecting values.

Returns string : Returns the joined string.When developing software, we often need to combine data efficiently and without repetition. This often comes up when manipulating listed data with the use Arrays.

However, in this article, we will be taking the mostly avoided path of handling matters ourselves. We will explore 3 ways to combine the elements of multiple arrays into one without any elements getting repeated. You should already have your development environment setup for this course. Open the cloned repository and inside the Beginner folder, navigate to the mergeArrays folder. Our work for this challenge will be done in here. Given two or more arrays, write a function that combines their elements into one array without any repetition.

To achieve this, we have to somehow detect the number of arrays provided and extract them individually before merging them into one array without any element repeating itself. Since we want to create a solution that can merge any number of arrays, the first step in solving this challenge is to dynamically detect and extract the arguments arrays our function receives and merge them into one. Functions receive values with which they carry out various operations in the form of arguments that are passed to them on call.

In like manner, our function receives the arrays to be combined as arguments. To access these arguments from within the function, JavaScript exposes an array-like object arguments which contains the values of all the arguments passed to that function. Thus we may access the arguments passed to the function as shown below:. Notice that in order to convert the arguments object to a real array, we directly create an array from it using the Array.

ES6 however offers us a cleaner and more concise way to achieve the same result using the rest parameter syntax which allows us to accept an infinite number of arguments as shown below:.

Using the … syntax above, we are able to combine all the arguments passed irrespective of the number into one array which we name arrays. Our console. The next step in solving this problem is combining the arrays received into one array still containing duplicates. To do this, we use a forEach loop to iterate through each array and add the elements therein into another array which we call jointArray. For each array, we use the spread operator to spread its elements as well as the elements in the jointArray which is initially empty into a new array.

We then reassign this array to jointArray. On complete execution of this statement, jointArray now contains all the elements from all the arrays received still with duplicates. Having covered the two steps common to every solution to this problem, we shall now examine the three ways to remove the duplicates from within our jointArray.

They are:. In the solution below we apply this concept in eliminating the duplicates within our joint array. Notice that we use the JavaScript spread operator once again to spread out all the elements of the jointArray into the new set.

This eliminates all duplicates as sets are designed to only hold unique values. We then spread the unique elements of the set back into an array which we return as the final result. Pretty simple, right? Another way to achieve this is by using the Array.PierBover kelabang perhaps something like:. This utilizes the ES6 rest parameters syntax This will create an array of arrays for as many array arguments you pass in.

Not to be confused with the identical looking spread syntax which is clearly used in the reducer. EliecerC FTW. EliecerC Booyaka Booyaka !! PierBover : for a generic number of arrays, an elegant way to do it :. Thumbs Up to EliecerC. All possible options, nuts for ya all!

Be aware that it's only taking into account the key you passed in your arguments to remove duplicates! One of the most important difference between the solutions, is that some methods doesn't mutate the original array i. Try this. I've noticed a quirk behavior with spread for flattening an array of arrays.

Skip to content.

lodash merge arrays without duplicates

Instantly share code, notes, and snippets. Code Revisions 1 Stars 99 Forks Embed What would you like to do? Embed Embed this gist in your website. Share Copy sharable link for this gist. Learn more about clone URLs. Download ZIP. Merge Arrays in one with ES6 Array spread. This comment has been minimized. Sign in to view. Copy link Quote reply. So how do you make that dynamic for any number of arrays? Nice, thanks, would rep up! This is so strange. Thanks for this!By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. With Lodash, how could I remove objects with duplicate id keys? Something with filter, map and unique, but not quite sure. Assuming that the data should be unique by id and your data is stored in data variable, you can use unique function like this:.

Or simply Use unionfor simple array. It creates duplicate-free version of an array. You can also use unionBy for 4. Learn more. Lodash remove duplicates from array Ask Question. Asked 4 years, 8 months ago.

Active 5 months ago. Viewed k times. My real data set is much larger and has more keys, but the concept should be the same. ChrisRich ChrisRich 5, 8 8 gold badges 31 31 silver badges 49 49 bronze badges. Active Oldest Votes. Ziv Weissman 3, 3 3 gold badges 19 19 silver badges 50 50 bronze badges.

Remove Duplicates from sorted Array

The lodash 4. Couldn't get the above example to work for the life of me using only uniq. With lodash 4. So as WillLovett said, we can use uniqBy to solve this problem. Oh boy. Why, oh why, is it uniq which is pronounced you-knee-queue instead of what it should be, unique Nov 29 '18 at Vixson Vixson 1 1 silver badge 3 3 bronze badges. I like this answer.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Code Golf Stack Exchange is a question and answer site for programming puzzle enthusiasts and code golfers.

It only takes a minute to sign up. I recently saw this Javascript code on StackOverflow for merging two arraysand removing duplicates:. Your challenge is to make an algorithm with less complexity. The winning criteria is the solution with the least complexitybut ties will be broken by shortest length in characters.

Package all your code together in a function that meets the following requirements for "correctness:".

How to merge two arrays in JavaScript and de-duplicate items

I'm not great at computing complexity but I believe this is O N. Would love if someone could clarify. Wasi's 8 character set implementation is better, if you don't think it violates the rules. To keep within the rules outlined above, I would use a similar strategy as the JavaScript solution and use a hash as an intermediary. This should run in O n time.

Subscribe to RSS

Please let me know if I've made any inaccurate statements or if I can improve the above answer either for efficiency or readability. Using memoization is probably unnecessary given that the keys to the hash are going to be unique and the values are irrelevant, so this is sufficient:. I really love Object tapbut we can accomplish the same result using Enumerable reduce :. A quick peek at the source of Arraythough, seems to confirm that using a hash as an intermediary seems to be the acceptable solution to performing a unique merge between 2 arrays.

This still can cast some doubts, if you want to distinguish and ''then this would not work. Could be 21, if overwriting global values is allowed it would remove my from the code. It returns elements in random order, because order doesn't matter.

As for complexity, on average it's O N depends on number of hash collisions, but they are rather rare - in worst case it can be O N 2 but this shouldn't happen, because Perl can detect pathological hashesand changes the hash function seed when it detects such behavior. Which not only looks infinitely better but will actually compile too long a line in its golfed form with the human-readable form:.

This should be O n as I copy a into c and then check each b against all of c. The last step is to eliminate the garbage that c will contain since it is uninitialized. I'm using ES6 generator. If you're looking for a JavaScript-based implementation that relies on the underlying Objects behind the framework to be efficient, I would've just used Set. Usually in an implementation, the Set object inherently handles unique objects during insertion with some sort of binary search indexing.

I know in Java it's a log n search, using binary search based on the fact that no set can contain a single object more than once. Try it online! If you know the complexity of the Set. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Array Merge without Duplicates Ask Question.You can use the JavaScript built in object Set to keep unique values of any type.

You can make use of ES6 Set to remove duplicate from an array. Here is how the code looks:. As seen in the above code, you created a set using the duplicate array. Creating a set itself eliminates duplicate entries from the array. Finally you converted the newly created Set to an Array using the Array. JavaScript filter method when applied on an array creates a new array which satisfies a particular condition.

You can use filter method to check for duplicates in array. Filter method callback takes in three arguments : current element, index of current element and the array being processed. Here is how you can use filter to remove duplicates:. As expected it would create a new array satisfying the condition specified in the callback function. The condition specified would satisfy only for unique elements and duplicates would be neglected, hence it would return an array with duplicates removed.

Lodash is a modern JavaScript utility library providing many utility methods in handy for direct in JavaScript applications. Along with the many set of utility functions that Lodash provides, it also has a method called uniq to remove duplicates from an array.

Lodash script methods are referenced using an underscore. Assuming that you have a JavaScript array with duplicates, you can remove the duplicates using uniq method as shown:.

The uniq method returns an array after removing duplicate elements from the passed in array. From the official documentation. In order to get started with Underscore.

lodash merge arrays without duplicates

Assuming that you have a JavaScript array with duplicate items, you can remove the duplicates using the method uniq provided by Underscore. In this tutorial, you saw different ways to remove duplicates from an array.