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Create array from an array with nested objects [duplicate]

I have an an array of tags linked to an article which contains nested objects:

[ {id: 1, name: {"en": "Tag 1" }}, {id: 2, name: {"en": "Tag 2" }}, {id: 3, name: {"en": "Tag 3" }} ]

I want to create a new array which simply shows the tag name is a single array:

[Tag 1, Tag 2, Tag 3]

I created the following method:

However, this creates an array of arrays:

How can I achieve the single array I want?

Button89's user avatar

3 Answers 3

you can replace :

Wandrille's user avatar

You could destructure the object and take en only for mapping.

var data = [{ id: 1, name: { en: "Tag 1" } }, { id: 2, name: { en: "Tag 2" } }, { id: 3, name: { en: "Tag 3" } }], result = data.map(({ name: { en } }) => en); console.log(result);

You could use map() to do that.

let data = [ {id: 1, name: {"en": "Tag 1" }}, {id: 2, name: {"en": "Tag 2" }}, {id: 3, name: {"en": "Tag 3" }} ]; let tags = data.map(item => item.name.en); console.log(tags);

Object.values() creates an array of values. So, in your code you could use flat() to convert the result to desired format.

let data = [ {id: 1, name: {"en": "Tag 1" }}, {id: 2, name: {"en": "Tag 2" }}, {id: 3, name: {"en": "Tag 3" }} ]; var tagNames = []; data.forEach(value => { tagNames.push(Object.values(value["name"])); }); console.log(tagNames.flat());

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Array.prototype.concat()

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

Arrays and/or values to concatenate into a new array. If all valueN parameters are omitted, concat returns a shallow copy of the existing array on which it is called. See the description below for more details.

Return value

A new Array instance.

Description

The concat method creates a new array. The array will first be populated by the elements in the object on which it is called. Then, for each argument, its value will be concatenated into the array — for normal objects or primitives, the argument itself will become an element of the final array; for arrays or array-like objects with the property Symbol.isConcatSpreadable set to a truthy value, each element of the argument will be independently added to the final array. The concat method does not recurse into nested array arguments.

The concat() method is a copying method . It does not alter this or any of the arrays provided as arguments but instead returns a shallow copy that contains the same elements as the ones from the original arrays.

The concat() method preserves empty slots if any of the source arrays is sparse .

The concat() method is generic . The this value is treated in the same way as the other arguments (except it will be converted to an object first), which means plain objects will be directly prepended to the resulting array, while array-like objects with truthy @@isConcatSpreadable will be spread into the resulting array.

Concatenating two arrays

The following code concatenates two arrays:

Concatenating three arrays

The following code concatenates three arrays:

Concatenating values to an array

The following code concatenates three values to an array:

Concatenating nested arrays

The following code concatenates nested arrays and demonstrates retention of references:

Concatenating array-like objects with Symbol.isConcatSpreadable

concat does not treat all array-like objects as arrays by default — only if Symbol.isConcatSpreadable is set to a truthy value (e.g. true ).

Using concat() on sparse arrays

If any of the source arrays is sparse, the resulting array will also be sparse:

Calling concat() on non-array objects

If the this value is not an array, it is converted to an object and then treated in the same way as the arguments for concat() . In this case the return value is always a plain new array.

Specifications

Browser compatibility.

BCD tables only load in the browser with JavaScript enabled. Enable JavaScript to view data.

Code Boxx

Simple Javascript Nested Array Examples – Create Push Pop Loop Check

Welcome to a quick tutorial on the nested array in Javascript. So you have finally met the worthy opponent called the multidimensional array, and this “array in an array” thing sure is confusing. How do we create one? Add elements to it? Find an element inside? Let us walk through some examples – Read on!

ⓘ I have included a zip file with all the example source code at the start of this tutorial, so you don’t have to copy-paste everything… Or if you just want to dive straight in.

TABLE OF CONTENTS

Download & notes.

Firstly, here is the download link to the example code as promised.

QUICK NOTES

Example code download.

Click here to download the source code, I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

NESTED ARRAY EXAMPLES

All right, let us now get into the various examples on how to work with a nested array in Javascript.

1) HOW TO DEFINE A NESTED ARRAY

When it comes to creating a nested array, some beginners immediately foam in the mouth and go on a “very difficult trance”. No idea why.

2) HOW TO ACCESS A NESTED ARRAY

When it comes to accessing a nested array, some beginners immediately go into brain freeze. No idea why. In this example:

If it is too confusing, think this way – let nested = arr[0] . Yep, nested is now referring to the nested array. Work on it as if it were a “flat array”.

3) NESTED ARRAY PUSH & POP

Nested arrays are still arrays. There’s nothing “special” about it, we can push() and pop() as usual. Of course, the many other functions and properties will also work – length , splice() , shift() , and unshift() .

4) LOOP OR TRAVERSE A NESTED ARRAY

Sadly, running through a nested array is not as simple as using a for loop… To traverse a nested array, we will have to use a recursive function.

5) CHECK IF VALUE EXIST IN A NESTED ARRAY

Yep – If you are looking to check if a value exists in a nested array, the usual ARRAY.find() will not quite work. We have to use a recursive function to check through all the elements again.

EXTRA BITS & LINKS

That’s all for the tutorial, and here is a small section on some extras and links that may be useful to you.

LINKS & REFERENCES

Thank you for reading, and we have come to the end. I hope that it has helped you to better understand, and if you want to share anything with this guide, please feel free to comment below. Good luck and happy coding!

1 thought on “Simple Javascript Nested Array Examples – Create Push Pop Loop Check”

This is the most useful tutorial about arrays in js I’ve ever found! Thank you

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Nested Arrays in JavaScript, Explained

You asked for it, we delivered. We explain nested arrays in a way that anyone, from beginner to expert, can understand.

javascript create array nested

The Array in JavaScript, as with arrays in other scripting and programming languages, is an object that lets you store multiple items in an ordered list, with each item having its own index.

Suppose you’re making a grocery list with apples, bananas, and oranges. Instead of storing each item in its own variable, you can store them in an array:

Since the array is an ordered list of items, each of the items in your groceryList array are assigned indices within it, starting at 0 and progressing in the order in which they were stored.

Respectively, “apples” would be assigned an index of 0, “bananas” an index of 1, and “oranges” an index of 2. Here’s how this looks like in terms of code:

You can try the above code out for yourself by inspecting this page right now and copy/pasting it into your browser’s console.

Nested Arrays

With JavaScript, you can also nest an Array inside an Array.

Suppose you wanted to sort the items in your groceryList array in three categories: fruits and vegetables.

This time, to make things understandable, we will populate our groceryList array with items in two steps.

First, we’ll declare an empty JavaScript array. Then, we’ll nest two arrays under it—one for fruits, the other for vegetables—and store the category in the zeroth index of each.

Take a peek at the code snippet below to see what exactly this looks like:

With this, we just nested two arrays, fruits and vegetables , under our groceryList array.

Another, more visual way to think about it is as a structured list with items and subitems:

We can access the items in the child array in a similar way as we’d do for the parent array:

Nested Arrays Within Nested Arrays

Another thing we can do is nest arrays under nested arrays.

Suppose we wanted to split the list of vegetables into fresh and frozen , then add tomatoes and cucumbers to fresh , and baby carrots and broccoli to frozen .

To achieve this, notice how we’re nesting an array under a nested array in line 6, again using the zeroth index for the category names ( fresh and frozen ):

Once again, the structure of our list evolved. We now have items, subitems, and subs of the subitems:

And, once again, we can access these by nesting the indexes in our statements:

You can then use all of JavaScript’s Array methods to perform actions on your nested arrays.

In Conclusion

Thank you for reading this far and I hoped this explanation, which I tried to make as simple and as beginner-friendly as possible, helped.

Newcomers to JavaScript are often intimidated by the concept of nested arrays because it sounds complicated. But, once you get the hang of it, it’s as simple as creating bulleted lists in Google Docs or working with tables in Google Sheets.

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Sanchithasr

Posted on Jan 5, 2021

Understanding Nested Arrays in JavaScript

An array is an ordered collection of values : each value is called an element , and each element has a numeric position in the array, known as its index .

JavaScript lets us create arrays inside array called Nested Arrays . Nested Arrays have one or many arrays as the element of an array. This might be little confusing in definition but it is very interesting once we dig inside.

javascript create array nested

Creating a Nested Array:

There are three syntax to create an array in JavaScript. Let’s create nested arrays using those three methods to get an idea of Nested Arrays. This one is just equating the variable to the array.

Second one is using the array method new Array() .

And the last one is using the Array() which is similar to the new Array() .

Note that all these methods yield the same result. Now that we know how to create the nested arrays, let’s see how to access the elements of the Nested Arrays.

Understanding how indices are assigned to the elements:

javascript create array nested

Similarly we can access any element with the help of index.

javascript create array nested

Flatten the nested Array:

There are ways to flatten the nested array. We can turn it into normal array by using the below methods.

1) Using the method Array.flat()

Array.flat() method produces a new array by concatenating all sub arrays recursively up to the depth you specify. Simply put, if you have an array of arrays (maybe more arrays within them), flat() will help you to join all entries together into a single array .

2) Using Array.toString() and String.split() methods

We can convert the array to string and the split it using .split() method. That way we get the array.

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After creating a JavaScript nested array, We can use the “push()” and “splice()” method for adding elements. Thanks for sharing. Saas vashikaran mantra

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Understanding Nested Arrays in JavaScript

By Sanchitha SR on Jan 4th, 2021

An array is an ordered collection of values: each value is called an element, and each element has a numeric position in the array, known as its index.

JavaScript lets us create arrays inside array called Nested Arrays . Nested Arrays have one or many arrays as the element of an array. This might be little confusing in definition but it is very interesting once we dig inside.

image

Creating a Nested Array

There are three syntax to create an array in JavaScript. Let's create nested arrays using those three methods to get an idea of Nested Arrays.

This one is just _equating _ the variable to the array .

Second one is using the array method new Array().

And the last one is using the Array() which is similar to the new Array() .

Note that all these methods yield the same result. Now that we know how to create the nested arrays, let's see how to access the elements of the Nested Arrays.mn

Understanding how indices is assigned to the elements

The arrays are listed according to the index. Below diagram explains how the indices are assigned to the elements in Nested Array.

image

Say we want to access the value 'Tangled' , we can navigate to it using this table.

image

Similarly we can access any element with the help of index.

Output from the console (console.table(favMovies))

Output from the console (console.table(favMovies))

Flatten the nested Array

There are ways to flatten the nested array. We can turn it into normal array by using the below methods.

1. Using the method Array.flat()

Array.flat() method produces a new array by concatenating all sub arrays recursively up to the depth you specify.

Simply put, if you have an array of arrays (maybe more arrays within them), flat() will help you to join all entries together into a single array.

2. Using Array.toString() and String.split() methods

We can convert the array to string and the split it using .split() method. That way we get the array.

And there we have it! I hope you found this useful. Thanks!

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Nested Arrays in JavaScript

10 June 2008 / 14 Comments

In previous tutorials we’ve taken a look at JavaScript array basics , manipulating arrays , and sorting arrays . So far, all the arrays we’ve dealt with have been “flat” arrays; each array element contains a single value, such as a number, string, or object.

However, like most programming languages, JavaScript lets you create arrays inside arrays, known as nested arrays . In a nested array, the elements of one array are themselves arrays. For example:

Here we’ve created an array of 2 elements. Each element is in turn an array containing 3 elements. To access the elements of the inner arrays, you simply use two sets of square brackets. For example, pets[1][2] accesses the 3rd element of the array inside the 2nd element of the pets array.

You can nest arrays as deeply as you like. For example, here we’ve created a top-level array called animals , into which we’ve placed the above pets array, as well as a similar dinosaurs array — that’s 3 levels of nesting in total:

Looping through nested arrays

Of course, once you start nesting arrays you quickly end up with lots of array elements. The easiest way to work with large arrays is to use loops . And in order to process nested arrays, you need to use nested loops.

For example, the following code loops through the animals nested array we created above, displaying each of the animals, along with their ages and types:

You now know how to create and use nested arrays in JavaScript. You’ll find nested arrays are useful when you want to store highly structured data — such as our animals example above — and when you’re creating multidimensional data structures (commonly used in games and graphics applications). Enjoy!

Reader Interactions

' src=

31 January 2013 at 1:25 pm

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19 March 2020 at 11:13 pm

Mr Matt you only put down the solution for your nested loop.. can u break it down in detail so some of us can really understand and apply .. thanks alot.

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18 April 2019 at 11:56 am

Imagine something like:

const newItem = [‘item 1’, ‘item 0’, ‘item 1’, ‘item 2’, ‘item 1’, ‘item 0’];

If I want to remove all ‘item 1’ I can use:

for(let i = newItem.length-1; i–;){ if (newItem[i] === “item 1”) newItem.splice(i, 1); }

The question is if I have an array inside another array how can I do? const newItem = [ [‘item 1’, ‘item 0’, ‘item 1’], [‘item 2’, ‘item 1’, ‘item 0’] ];

' src=

29 April 2019 at 11:44 pm

Nested loops should do the trick. Place a for loop inside another for loop. The outer loop iterates though the items in the outer array; the inner loop iterates through the items in the inner arrays.

' src=

26 February 2020 at 6:55 pm

@Toni, You may want to use nested loop like,

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15 April 2020 at 11:17 am

Hi Mat, I got a trick problem. I extract from two differen Databases in different environments Data to arrays. I merge this two arrays an get a wrong json . The content ist there as

If I read the result

Same problem I have when I get the result in TWO Arrays like

15 April 2020 at 11:26 am

Can you post the full code on something like https://codesandbox.io so I can see the problem?

' src=

16 April 2020 at 6:12 am

I load a zip with all informatios on my server. you can download it here.

http://dmdg.io/dmdg.zip

Hope the errordescription gave you all information yo need.

Kind regards Gert

' src=

5 November 2020 at 4:49 pm

How i can print all the elements array. For example: Input: Let arr= [1,2,[3,4,[5,6,7]]]; Output : 1234567

' src=

30 June 2021 at 4:22 pm

[1,2,[3,4,[5,6,7]]].flat(Infinity).join(“”); // 1234567

' src=

4 October 2021 at 2:33 pm

var = arr [[{},{},{}],[{},{},{}],[{},{},{}],[{},{},{}],[{},{},{}],]; how to access inside of obj name etc

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10 November 2021 at 2:22 pm

Very helpful. Thank you!

' src=

18 January 2022 at 4:15 am

I could kiss you!! LOL. A whole day to discover you…

' src=

21 March 2023 at 7:03 am

I have a question EmpList[{“key”:”value”, “key1″:”value1”},{“firstname”:”lastname”}];

How do I get details of value and lastname.

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JavaScript 2D Array – Two Dimensional Arrays in JS

In JavaScript programming, we are all used to creating and working with one-dimensional arrays. These are arrays that contain elements (elements of similar data types or multiple data types).

But it’s also good to know that two-dimensional arrays (2D arrays) exist in JS.

In this article, you will learn what two-dimensional arrays are and how they work in JavaScript. It is quite different from other programming languages because, technically, there is no two-dimensional array in JavaScript.

What is a Two-Dimensional Array?

A two-dimensional array, also known as a 2D array, is a collection of data elements arranged in a grid-like structure with rows and columns. Each element in the array is referred to as a cell and can be accessed by its row and column indices/indexes.

In JavaScript, there is no direct syntax for creating 2D arrays as with other commonly used programming languages like C, C++, and Java.

You can create two-dimensional arrays in JavaScript through jagged arrays — an array of arrays. For example, below is what a jagged array looks like:

But there is a limitation. It is important to note that two-dimensional arrays have a fixed size. This means that once they are created, the number of rows and columns should be fixed. Also, each row should have a similar number of elements (columns).

For example, the array below has three rows and four elements:

The limitation is that with jagged arrays, you don't get to specify a fixed row and column. This means that a jagged array could have m rows, each having different numbers of elements.

Why Use a 2D Array in JavaScript?

At this point, you may ask yourself about the importance of a 2D array, especially if this is your first time reading about 2D arrays.

In JavaScript, we use two-dimensional arrays, also known as matrices, to store and manipulate data in a structured and organized manner.

How to Access Elements in a JavaScript 2D Array

Before you learn how to create 2D arrays in JavaScript, let’s first learn how to access elements in 2D arrays.

You can access the elements of a two-dimensional array using two indices, one for the row and one for the column. Suppose you have the following two-dimensional array:

The above is a jagged array in which each element holds the student's name, test score, exam score, and grade. You can access specific elements using the row and column index as seen in the syntax below:

To better understand this, let’s convert the two-dimensional array above to a table using console.table(arrayName) .

Note: make sure that you replace arrayName with the name of your 2D array. In my case, it is MathScore .

You will get an output like this, showing the row and column index. Remember that arrays are zero-indexed, meaning items are referenced from 0, not 1.

s_357699FE5D3810E96F0B6815928F66401CBB5DFE39FAA8BDA7338BEC543A022F_1673843651418_Untitled.drawio+3

Please note that the (index) column and row are for the illustration that indicates the indices/indexes of the inner array.

You use two square brackets to access an element of the two-dimensional or multi-dimensional array. The first accesses the rows, while the second accesses the element in the specified row.

How to access the first and last elements of a 2D array

Sometimes you might need to find the first and last elements of a two-dimensional array. You can do this using the first and last index of both the rows and columns.

The first element will always have the row and column index of 0, meaning you will use arrayName[0][0], .

The index of the last element can be tricky, however. For example, in the example above, the first element is ‘John Doe’ while the last is ‘B’:

How to add all elements of a 2D array

In some situations, all the elements of your 2D array can be numbers, so you may need to add them together and arrive at just one digit. You can do this using a nested loop. You will first loop through the rows, then, for each row, you loop through its elements.

How to Manipulate 2D Arrays in JavaScript

You can manipulate 2D arrays just like one-dimensional arrays using general array methods like pop, push, splice and lots more.

Let’s start by learning how to add/insert a new row and element to the 2D array.

How to insert an element into a 2D array

You can add an element or many elements to a 2D array with the push() and unshift() methods.

The push() method adds elements(s) to the end of the 2D array, while the unshift() method adds element(s) to the beginning of the 2D array.

When you console.log() or console.table() the array, you will see that the new rows have been added:

You can also add elements to the inner array, but it’s wrong to push to just one inner array without affecting all the array elements. This is because two-dimensional arrays are meant to have the same number of elements in each element array.

Instead of affecting one array element, you can add elements to all element arrays at once:

This will return:

You can also use the unshift() method to insert the element at the beginning and the splice() method to insert at the middle of the array:

In the above, 1 is the position where you want the new array to be inserted (remember it is zero-indexed), 0 is used so it removes no element, and then the third parameter is the array to be added.

This is the output:

How to remove an element from a 2D array

You can also remove element(s) from the beginning and end of a 2D array with the pop() and shift() methods. This is similar to how the push() and unshift() methods work, but you do not add any parameters to the methods this time.

When you console.log() or console.table() the array, you will see that the first and last array elements have been removed:

You can also remove elements from each array element:

You can also use the shift() method to remove the element at the beginning and the splice() method to remove array elements from specific positions:

In the code above, you remove one item from position index 2 of the MathScore 2D array. This will output:

Note: All JavaScript array methods will operate on a 2D array because it is an array of arrays. You only have to be mindful when adjusting individual elements in the elements array. You make a similar change on all elements by looping through, even though 2D arrays in JavaScript are not strict.

How to Create 2D Arrays in JavaScript

There are two options for creating a multi-dimensional array. You can create the array manually with the array literal notation, which uses square brackets [] to wrap a list of elements separated by commas. You can also use a nested loop.

How to create a 2D array using an array literal

This is just like the examples we have been considering using the following syntax:

For example, below is a 2D array that holds information about each student’s math score and grade:

How to create a 2D array using a nested for loop

There are many approaches to doing this. But generally, you create a nested loop where the first loop will loop through the rows while the second loop will loop through the elements in the inner array (columns):

In the code above, you will first loop through the rows. For each row, it will create an empty array within the original array declared and stored in variable arr . You will then create a nested loop to loop through the columns and add individual elements.

In this example, the index for j is used and will output:

You can decide to create a number, initialize with 0, and then increase as you loop through so you don’t have the same number for all elements:

You can also decide to create a function that accepts these values as arguments:

How to Update Elements in 2D Arrays in JavaScript

This is very similar to how you do it with one-dimensional arrays, where you can update an array’s value by using the index to assign another value.

You can use the same approach to change an entire row or even individual elements:

This will replace the value of index 1 with this new array:

You can update individual elements by tracking the row and column indices and updating their values:

This will change the name on the row with index 2 to “Jack Jim”, as seen below:

Wrapping Up

In this article, you have learned what two-dimensional arrays are and how they work in JavaScript.

It’s important to know that 2D arrays in JavaScript still work very much like one-dimensional arrays, so feel free to tweak and manipulate them with JavaScript methods .

Have fun coding!

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JavaScript: 3 Ways to Create Multidimensional Arrays

A multidimensional array is an array that contains one or more arrays as elements. In other words, it is an array of arrays. Among multidimensional arrays, two-dimensional arrays (or 2D arrays) are widely used because they can represent many types of data that have a grid-like or tabular structure. Their elements are organized into rows and columns

This article walks you through a couple of different ways to create multidimensional arrays in JavaScript.

Using square brackets (the array literal notation)

JavaScript does not have a built-in syntax for multidimensional arrays, but you can create them by using an array of arrays.

For example, you can create a 2D array with 3 rows and 4 columns like so:

You can access and modify the elements of a multidimensional array by using indexes. For instance, to get the value of 6 from the above array, you can use array[1][1] . To change it to 10 , you can use array[1][1] = 10 .

This example shows how to create a three-dimensional array (3D array) in JavaScript:

Using the Array() constructor

The preceding approach seems neat and intuitive. However, it isn’t the only possible way. You can also use the new Array() constructor to create an array and then assign each element as another array.

Using nested loops

You can make use of nested loops to create an empty multidimensional array and then fill it with values. This techniqeu is useful when you need to programmatically create an array with a large number of rows and columns.

Output (yours might be different from mine because the code use Math.random() ):

You’ve learned some distinct ways to make new multidimensional arrays in JavaScript. They are very versatile and efficient for storing and manipulating complex data, especially numeric data.

If you find errors or anachronisms in the code examples, please let me know by leaving comments. I will review and update them as soon as possible. Happy JavaScripting & have a nice day!

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