Run the above code. You will get the order 1, 15, 2. This is because the method converts everything to a string and uses the default lexicographic order.

In the previous article, we talked about what it is and how to work with it. In this article we will talk about multidimensional array.

It is an array that has one or more elements, which are also arrays. Depending on the depth of the ad, in particular, it may be called two-dimensional array(2 levels) either three-dimensional array(3 levels) either four-dimensional(4 levels) and so on.

The most popular, after a one-dimensional array, which is most often used is a two-dimensional array. We will study it in more detail.

As you can see, the elements of a two-dimensional array are one-dimensional arrays. If these one-dimensional arrays contained more arrays, then the arr array would already be three-dimensional.

For example, let's create three simple arrays and fill them with data. We will fill the first with even numbers, the second with odd numbers, and the third with some arbitrary data.

// Declare three empty arrays var evenNumbers = new Array (); // Variable k - for array indices evenNumbers var k = 0; var oddNumbers = new Array (); // Variable n - for array indices oddNumbers var n = 0; var data = new Array ("car", "plane", true, 89, "m"); // Fill the array evenNumbers, with even numbers for (var i = 1; i

In order to see what is inside the array, you can use a tool such as console.

For example, we want to see the contents of an array with odd numbers oddNumbers. To do this, write the following line in the code below:

Console.log (oddNumbers);

To see the result, you need to open console in browser... In Google Chrome, this is done like this: right-click on the page, and from the context menu, select the last option “View code”, that is, the inspector. In the English version, this option is called Inspect.

And below the developer toolbar will appear. In it, you need to go to the Console tab.

Now in order to create a two dimensional array, you need to declare it, and add the one-dimensional arrays that you created above to it.

// Declare a two-dimensional array twoDimens, and fill it var twoDimens = new Array (evenNumbers, oddNumbers, data); console.log (twoDimens);

Let's see the contents of this array in the console.

iterating over a two-dimensional array

First, let's learn how to access the elements of a two-dimensional array.

As with single arrays, elements are accessed by their indices.

For example, let's display the element at index 3 from an array with odd numbers (oddNumbers). The index of the one-dimensional array oddNumbers in the two-dimensional array twoDimens is one (1).

Document.write ("The element with index 3 from the array of odd numbers oddNumbers is:" + twoDimens); // Element: 7

In the array twoDimens, we refer to the element at index 1. The element at that index is the oddNumbers array. And in this array, we are already accessing the element with index 3, which is the number 7.

Now let's get down to the question itself how to iterate over a two dimensional array.

Loop over a two-dimensional array is done using a double loop. For example, let's iterate over our twoDimens array.

For (var i = 0; i< twoDimens.length; i++){ for(var j = 0; j < twoDimens[i].length; j++){ document.write("

Element with index "+ i +" "+ j +" is equal to: "+ twoDimens [i] [j] +"

In the first loop, we iterate over the twoDimens array itself. In the second loop, we are already iterating over the element itself (array). First, the variable i is equal to 0. Therefore, in the second loop, we first iterate over the first array evenNumbers, which has index 0. And already inside the second loop, we access the elements of this array. Thus: twoDimens [j]. Where j ranges from 0 to the length of the evenNumbers array.

After iterating over the elements from the first array, we return to the first loop, increment the variable i, and proceed to iterate over the second array oddNumbers, which has index 1. And so, we iterate over each element of the two-dimensional array twoDimens.

Now let's look at the result of this search:

That's all I wanted to talk about in this article. Now you know how to create a two-dimensional array, how to access the elements of a two-dimensional array, and how to iterate over a two-dimensional array. I hope everything was clear. I wish you great success!

Arrays

Array is an ordered collection of values. The values ​​in an array are called elements, and each element is characterized by a numeric position in the array, which is called an index. Arrays in JavaScript are untyped: the elements of an array can be of any type, and different elements of the same array can be of different types. Array elements can even be objects or other arrays, allowing you to create complex data structures such as arrays of objects and arrays of arrays.

Array indices in JavaScript are zero-based and use 32-bit integers — the first element of an array has index 0. JavaScript arrays are dynamic: they can grow and shrink as needed; there is no need to declare fixed sizes of arrays when they are created or to re-allocate memory when they are resized.

Arrays in JavaScript are a specialized form of objects, and array indices mean little more than just property names, which coincidentally are integers.

Creating arrays

The easiest way to create an array is with a literal, which is a simple comma-separated list of array elements in square brackets. The values ​​in an array literal do not have to be constants - they can be any expressions, including object literals:

Var empty =; // Empty array var numbers =; // Array with five numeric elements var misc = [1.1, true, "a",]; // 3 elements of different types + trailing comma var base = 1024; var table =; // Array with variables var arrObj = [,]; // 2 arrays inside containing objects

The array literal syntax allows you to insert an optional trailing comma, i.e. literal [,] matches an array with two elements, not three.

Another way to create an array is to call the constructor Array ()... The constructor can be called in three different ways:

Call the constructor with no arguments:

Var arr = new Array ();

In this case, an empty array equivalent to the literal will be created.

Call the constructor with a single numeric argument specifying the length of the array:

Var arr = new Array (10);

In this case, an empty array of the specified length will be created. This form of calling the Array () constructor can be used to pre-allocate memory for an array if the number of its elements is known in advance. Note that this does not store any values ​​in the array.

Explicitly specify the values ​​of the first two or more array elements or one non-numeric element in a constructor call:

Var arr = new Array (5, 4, 3, 2, 1, "test");

In this case, the arguments of the constructor become the values ​​of the elements of the new array. Using array literals is almost always easier than using the Array () constructor in this way.

Reading and writing array elements

Array elements are accessed using the operator. There must be an array reference to the left of the parentheses. An arbitrary expression that returns a non-negative integer value must be inside the parentheses. This syntax is suitable for both reading and writing the value of an array element. Therefore, all of the following JavaScript statements are valid:

// Create an array with one element var arr = ["world"]; // Read item 0 var value = arr; // Write the value to element 1 arr = 3.14; // Write a value to element 2 i = 2; arr [i] = 3; // Write a value to element 3 arr = "hello"; // Read items 0 and 2, write the value to item 3 arr] = arr;

Let me remind you that arrays are a specialized kind of object. The square brackets used to access array elements act exactly the same as the square brackets used to access the properties of an object. The JavaScript interpreter converts the numeric indices in parentheses to strings - index 1 becomes the string "1" - and then uses the strings as property names.

There is nothing special about converting numeric indices to strings: the same can be done with regular objects:

Var obj = (); // Create a simple object obj = "one"; // Index it with integers

The peculiarity of arrays is that when using property names that are non-negative integers, the arrays automatically determine the value of the property length... For example, the arr array was created above with a single element. Then, values ​​were assigned to its elements with indices 1, 2, and 3. As a result of these operations, the value of the length property of the array changed and became equal to 4.

You should clearly distinguish between indexes in an array and object property names. All indexes are property names, but only properties with integer names are indexes. All arrays are objects, and you can add properties to them with any name. However, if you touch properties that are array indices, arrays react by updating the value of the length property as needed.

Note that negative and non-integers are allowed as array indices. In this case, numbers are converted to strings, which are used as property names.

Adding and Removing Array Elements

We have already seen that the easiest way to add elements to an array is to assign values ​​to new indices. You can also use the method to add one or more elements to the end of an array push ():

Var arr =; // Create an empty array arr.push ("zero"); // Add a value to the end arr.push ("one", 2); // Add two more values

You can also add an element to the end of an array by assigning a value to the arr element. To insert an element at the beginning of an array, you can use the method unshift () and the existing elements in the array are shifted to the higher indices.

You can delete elements of an array using the delete operator, like ordinary properties of objects:

Var arr =; delete arr; 2 in arr; // false, index 2 in the array is undefined arr.length; // 3: the delete operator does not change the length property of the array

Removing an element is similar (but slightly different) assigning an undefined value to that element. Note that applying the delete operator to an element in an array does not change the value of the length property, nor does it move down the elements with higher indices to fill the void left after the element is deleted.

In addition, it is possible to remove elements at the end of an array by simply assigning a new value to the length property. Arrays have a method pop ()(opposite to push ()), which decreases the length of the array by 1 and returns the value of the removed element. There is also a method shift ()(opposite to unshift ()), which removes the element at the beginning of the array. Unlike the delete operator, the shift () method shifts all elements down one position below their current indices.

Finally, there is a multipurpose method splice (), which allows you to insert, delete, and replace elements of arrays. It changes the value of the length property and shifts the elements of the array with lower or higher indices as needed. We will discuss all these methods a little later.

Multidimensional arrays

JavaScript does not support "real" multidimensional arrays, but it does a good job of mimicking them using arrays from arrays. To access a data item in an array of arrays, it is sufficient to use the operator twice.

For example, suppose the variable matrix is ​​an array of arrays of numbers. Each element of matrix [x] is an array of numbers. You can use the expression matrix [x] [y] to access a specific number in an array. Below is a specific example where a two-dimensional array is used as a multiplication table:

// Create a multidimensional array var table = new Array (10); // There are 10 rows in the table for (var i = 0; i

Array Class Methods

The ECMAScript 3 standard defines many convenient functions for working with arrays as part of Array.prototype, which are available as methods of any array. These methods will be presented in the following subsections.

Join () method

The Array.join () method converts all the elements in the array to strings, concatenates them, and returns the resulting string. An optional argument can be passed to the method with a string that will be used to separate the elements in the result string. If no delimiter string is specified, a comma is used. For example, the following snippet results in the string "1,2,3":

Var arr =; arr.join (); // "1,2,3" arr.join ("-"); // "1-2-3"

The reverse () method

The Array.reverse () method reverses the order of the elements in an array and returns a reordered array. The permutation is done directly on the original array, i.e. this method does not create a new array with reordered elements, but reorders them in an already existing array. For example, the following snippet, which uses the reverse () and join () methods, results in the string "3,2,1":

Var arr =; arr.reverse (). join (); // "3,2,1"

Sort () method

The Array.sort () method sorts the elements in the original array and returns the sorted array. If the sort () method is called with no arguments, sorting is done alphabetically (for comparison, items are temporarily converted to strings if necessary). Undefined elements are wrapped to the end of the array.

You can pass a comparison function as an argument to sort () to sort in any other non-alphabetical order. This function sets which of its two arguments should come first in the sorted list. If the first argument must precede the second, the comparison function must return a negative number. If the first argument is to follow the second in the sorted array, then the function must return a number greater than zero. And if two values ​​are equivalent (i.e. the order is not important), the comparison function should return 0:

Var arr =; arr.sort (); // Alphabetical order: 1111, 222, 33, 4 arr.sort (function (a, b) (// Numeric order: 4, 33, 222, 1111 return ab; // Returns the value 0 // depending on the sort order a and b)); // Sort backwards, from highest to lowest arr.sort (function (a, b) (return b-a));

Notice how convenient it is to use an unnamed function in this snippet. The comparison function is only used here, so there is no need to give it a name.

The concat () method

The Array.concat () method creates and returns a new array containing the elements of the original array on which the concat () method was called and the values ​​of any arguments passed to the concat () method. If any of these arguments are themselves an array, its elements are added to the returned array. It should be noted, however, that there is no recursive conversion of an array from arrays to a one-dimensional array. The concat () method does not modify the original array. Below are some examples:

Var arr =; arr.concat (4, 5); // Returns arr.concat (); // Returns arr.concat (,) // Returns arr.concat (4,]) // Returns]

Slice () method

The Array.slice () method returns a slice, or subarray, of the specified array. The two arguments to the method define the start and end of the returned chunk. The returned array contains the element numbered in the first argument plus all subsequent elements up to (but not including) the element numbered in the second argument.

If only one argument is specified, the returned array contains all elements from the start position to the end of the array. If any of the arguments are negative, it specifies the element number relative to the end of the array. So, argument -1 corresponds to the last element of the array, and argument -3 corresponds to the third element of the array from the end. Here are some examples:

Var arr =; arr.slice (0.3); // Returns arr.slice (3); // Returns arr.slice (1, -1); // Returns arr.slice (-3, -2); // Will return

Splice () method

The Array.splice () method is a generic method that inserts or removes elements from an array. Unlike the slice () and concat () methods, the splice () method modifies the original array on which it was called. Note that the splice () and slice () methods have very similar names but perform completely different operations.

The splice () method can remove elements from an array, insert new elements, or do both at the same time. The elements of the array are shifted as necessary so that after insertion or deletion, a contiguous sequence is formed.

The first argument to the splice () method specifies the position in the array from which to insert and / or delete. The second argument specifies the number of elements to be removed (cut) from the array. If the second argument is omitted, all array elements from the specified array to the end of the array are removed. The splice () method returns an array of the removed elements, or (if none of the elements have been removed) an empty array.

The first two arguments to the splice () method specify the array elements to remove. These arguments can be followed by any number of additional arguments specifying the elements to be inserted into the array, starting at the position specified in the first argument.

Var arr =; arr.splice (4); // Returns arr = arr.splice (1,2); // Returns arr = arr.splice (1,1); // Will return; arr = arr =; arr.splice (2,0, "a", "b"); // Will return; arr =

The push () and pop () methods

The push () and pop () methods allow arrays to be treated like stacks. The push () method adds one or more new elements to the end of the array and returns its new length. The pop () method performs the opposite operation - it removes the last element of the array, decreases the length of the array, and returns the value it removed. Note that both of these methods modify the original array rather than creating a modified copy of it.

The unshift () and shift () Methods

The unshift () and shift () methods behave in much the same way as push () and pop (), except that they insert and remove elements at the beginning of the array, not at the end. The unshift () method shifts existing elements towards larger indices to make room, adds the element or elements to the beginning of the array, and returns the new length of the array. The shift () method removes and returns the first element of the array, shifting all subsequent elements down one position to occupy the space vacated at the beginning of the array.

Last update: 09.04.2018

Arrays are intended for working with datasets. The expression new Array () is used to create an array:

Var myArray = new Array ();

There is also a shorter way to initialize an array:

Var myArray =;

In this case, we are creating an empty array. But you can also add initial data to it:

Var people = ["Tom", "Alice", "Sam"]; console.log (people);

In this case, the myArray will have three elements. Graphically, it can be represented as follows:

Indexes are used to refer to individual elements of an array. The counting starts from zero, that is, the first element will have index 0, and the last one will have index 2:

Var people = ["Tom", "Alice", "Sam"]; console.log (people); // Tom var person3 = people; // Sam console.log (person3); // Sam

If we try to access an element at an index greater than the size of the array, we get undefined:

Var people = ["Tom", "Alice", "Sam"]; console.log (people); // undefined

Also, by the index, the values ​​for the array elements are set:

Var people = ["Tom", "Alice", "Sam"]; console.log (people); // Tom people = "Bob"; console.log (people); // Bob

Moreover, unlike other languages ​​like C # or Java, you can install an element that was not initially installed:

Var people = ["Tom", "Alice", "Sam"]; console.log (people); // undefined - there are only three elements in the array people = "Bob"; console.log (people); // Bob

It is also worth noting that, unlike a number of programming languages ​​in JavaScript, arrays are not strongly typed, one array can store data of different types:

Var objects = ["Tom", 12, true, 3.14, false]; console.log (objects);

spread operator

The spread operator ... allows you to take values ​​from an array separately:

Let numbers =; console.log (... numbers); // 1 2 3 4 console.log (numbers); //

The spread operator is specified before the array. As a result, the expression ... numbers will return a set of numbers, but it will not be an array, but individual values.

Multidimensional arrays

Arrays can be one-dimensional and multi-dimensional. Each element in a multidimensional array can be a separate array. Above we considered a one-dimensional array, now let's create a multidimensional array:

Var numbers1 =; // one-dimensional array var numbers2 = [,]; // two-dimensional array

Visually, both arrays can be represented as follows:

One-dimensional array numbers1

To get a single element of an array, an index is also used:

Var tomInfo = people;

Only now the tomInfo variable will represent an array. To get an element inside a nested array, we need to use its second dimension:

Console.log ("Name:" + people); // Tom console.log ("Age:" + people); // 25

That is, if we can visually represent a two-dimensional array in the form of a table, then the people element will refer to the table cell, which is located at the intersection of the first row and the second column (the first dimension is 0 - a row, the second dimension - 1 - a column).

We can also do the assignment:

Var people = [["Tom", 25, false], ["Bill", 38, true], ["Alice", 21, false]]; people = 56; // assign a separate value console.log (people); // 56 people = ["Bob", 29, false]; // assign an array console.log (people); // Bob

When creating multidimensional arrays, we are not limited to only two-dimensional ones, but we can also use large-dimensional arrays:

Var numbers =; numbers =; // now numbers is a two-dimensional array numbers =; // now numbers is a three-dimensional array numbers = 5; // the first element of the 3D array is 5 console.log (numbers);

Greetings to everyone interested in JavaScript multidimensional arrays and sorting. In the current publication, I will try to cover this topic in all details.

Therefore, after reading this article, you will learn why multidimensional arrays are used in web applications, how they are created, and how they can be manipulated and sorted. Let's get down to learning!

How are multidimensional arrays created and what are they for?

To begin with, it's worth remembering how a regular one-dimensional array is created.

var array =

Now, remember that a multidimensional array is an array of arrays. I agree, it sounds like a tautology. However, read the definition again. Indeed, a multidimensional array consists of a certain number of nested ones.

Consider the following situation. At the beginning of a game, the user enters his name, and after the end, a rating table with the names of the players and their records is displayed on the screen.

It is clear that such information is stored in a database. But when we pull it out of the database, we get a multidimensional array. After all, each subarray contains the player's login and the number of points scored.

It will all look like this:

var results = [["Markus", 333], ["Natasha", 211], ["Alexey", 124]];

As you can see, information can be stored heterogeneous. It can be strings, numbers, and even. This is possible because the arrays in are untyped.

In this case, access to elements occurs through a double operator.

To consolidate the material, analyze a small program.

Results =

Arrays are a fairly convenient way to store ordered complex data while processing them. In addition, it is very convenient to work with them and, at the same time, the speed of their processing is quite high.

Data sorting methods

For arrays in JavaScript, there is a built-in method called sort ()... This tool is very flexible. And now I'll explain why.

If you use a method with no parameters, then it automatically orders the subarrays by the first element in alphabetical order. So, when calling results.sort () the parsed object will look like this:

Alexey, 124

Markus, 333

Natasha, 211

And if you swap the elements in each nested array, you get:

124, Alexey

211, Natasha

333, Markus

In this case, for comparison, all elements are temporarily converted to strings.

If, to solve a specific task, you need a function that sorts elements in a non-standard way, then you can write it yourself and pass it as a parameter to sort ()... It should be borne in mind that a user-defined function must return:

• a positive number (generally choose 1) if the first specified item follows the second in the comparison;
• a negative number (usually -1) if the second selected item should follow the first;
• zero if the two tested values ​​are equal.

As an example, let's take the initial array results sort by points. Moreover, the results will be sorted from highest to lowest. This can be done in two ways.

In the first version, I changed the sorting logic, i.e. in a situation where it is necessary to return a positive number, I return a negative one and vice versa.

Record table:

But in the second method, I left the sorting logic intact, but additionally used another method - reverse ()... As the name suggests, reverse reverses the order of the elements.

Therefore, the sort () function will look like this:

function RecordSort (a, b) (if (a> b) return 1; else if (a< b) return -1; else return 0; }

After that, let's add the above method.

The conclusion is made in a similar way.

I want to draw your attention to one important point. When using these functions, all changes occur to the array to which you apply them. Thus, if you need to preserve the original form of the data, then create a copy, and then edit it.

Well, so I talked about multidimensional arrays and their sorting. If you liked the article, then subscribe to the blog and read other equally interesting publications. I would be grateful for the reposts. Until next time!

Bye Bye!

Best regards, Roman Chueshov