Get item from javascript array

JavaScript Arrays

An array is a special variable, which can hold more than one value:

Why Use Arrays?

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

An array can hold many values under a single name, and you can access the values by referring to an index number.

Creating an Array

Using an array literal is the easiest way to create a JavaScript Array.

It is a common practice to declare arrays with the const keyword.

Learn more about const with arrays in the chapter: JS Array Const.

Example

Spaces and line breaks are not important. A declaration can span multiple lines:

Example

You can also create an array, and then provide the elements:

Example

Using the JavaScript Keyword new

The following example also creates an Array, and assigns values to it:

Example

The two examples above do exactly the same.

There is no need to use new Array() .

For simplicity, readability and execution speed, use the array literal method.

Accessing Array Elements

You access an array element by referring to the index number:

Note: Array indexes start with 0.

[0] is the first element. [1] is the second element.

Changing an Array Element

This statement changes the value of the first element in cars :

Example

Converting an Array to a String

The JavaScript method toString() converts an array to a string of (comma separated) array values.

Example

const fruits = [«Banana», «Orange», «Apple», «Mango»];
document.getElementById(«demo»).innerHTML = fruits.toString();

Access the Full Array

With JavaScript, the full array can be accessed by referring to the array name:

Example

Arrays are Objects

Arrays are a special type of objects. The typeof operator in JavaScript returns «object» for arrays.

But, JavaScript arrays are best described as arrays.

Arrays use numbers to access its «elements». In this example, person[0] returns John:

Array:

Objects use names to access its «members». In this example, person.firstName returns John:

Object:

Array Elements Can Be Objects

JavaScript variables can be objects. Arrays are special kinds of objects.

Because of this, you can have variables of different types in the same Array.

You can have objects in an Array. You can have functions in an Array. You can have arrays in an Array:

Array Properties and Methods

The real strength of JavaScript arrays are the built-in array properties and methods:

Array methods are covered in the next chapters.

The length Property

The length property of an array returns the length of an array (the number of array elements).

Example

The length property is always one more than the highest array index.

Accessing the First Array Element

Example

Accessing the Last Array Element

Example

Looping Array Elements

One way to loop through an array, is using a for loop:

Example

const fruits = [«Banana», «Orange», «Apple», «Mango»];
let fLen = fruits.length;

You can also use the Array.forEach() function:

Example

const fruits = [«Banana», «Orange», «Apple», «Mango»];

Adding Array Elements

The easiest way to add a new element to an array is using the push() method:

Example

const fruits = [«Banana», «Orange», «Apple»];
fruits.push(«Lemon»); // Adds a new element (Lemon) to fruits

New element can also be added to an array using the length property:

Example

const fruits = [«Banana», «Orange», «Apple»];
fruits[fruits.length] = «Lemon»; // Adds «Lemon» to fruits

Adding elements with high indexes can create undefined «holes» in an array:

Example

const fruits = [«Banana», «Orange», «Apple»];
fruits[6] = «Lemon»; // Creates undefined «holes» in fruits

Associative Arrays

Many programming languages support arrays with named indexes.

Arrays with named indexes are called associative arrays (or hashes).

JavaScript does not support arrays with named indexes.

In JavaScript, arrays always use numbered indexes.

Example

const person = [];
person[0] = «John»;
person[1] = «Doe»;
person[2] = 46;
person.length; // Will return 3
person[0]; // Will return «John»

WARNING !!
If you use named indexes, JavaScript will redefine the array to an object.

After that, some array methods and properties will produce incorrect results.

Example:

const person = [];
person[«firstName»] = «John»;
person[«lastName»] = «Doe»;
person[«age»] = 46;
person.length; // Will return 0
person[0]; // Will return undefined

The Difference Between Arrays and Objects

In JavaScript, arrays use numbered indexes.

In JavaScript, objects use named indexes.

Arrays are a special kind of objects, with numbered indexes.

When to Use Arrays. When to use Objects.

• JavaScript does not support associative arrays.
• You should use objects when you want the element names to be strings (text).
• You should use arrays when you want the element names to be numbers.

JavaScript new Array()

JavaScript has a built-in array constructor new Array() .

But you can safely use [] instead.

These two different statements both create a new empty array named points:

These two different statements both create a new array containing 6 numbers:

The new keyword can produce some unexpected results:

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Array.prototype.find()

The find() method returns the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned.

• If you need the index of the found element in the array, use findIndex() .
• If you need to find the index of a value, use indexOf() . (It’s similar to findIndex() , but checks each element for equality with the value instead of using a testing function.)
• If you need to find if a value exists in an array, use includes() . Again, it checks each element for equality with the value instead of using a testing function.
• If you need to find if any element satisfies the provided testing function, use some() .

Try it

Syntax

find(callbackFn) find(callbackFn, thisArg) 

Parameters

A function to execute for each element in the array. It should return a truthy value to indicate a matching element has been found, and a falsy value otherwise. The function is called with the following arguments:

The current element being processed in the array.

The index of the current element being processed in the array.

The array find() was called upon.

A value to use as this when executing callbackFn . See iterative methods.

Return value

The first element in the array that satisfies the provided testing function. Otherwise, undefined is returned.

Description

The find() method is an iterative method. It calls a provided callbackFn function once for each element in an array in ascending-index order, until callbackFn returns a truthy value. find() then returns that element and stops iterating through the array. If callbackFn never returns a truthy value, find() returns undefined .

callbackFn is invoked for every index of the array, not just those with assigned values. Empty slots in sparse arrays behave the same as undefined .

find() does not mutate the array on which it is called, but the function provided as callbackFn can. Note, however, that the length of the array is saved before the first invocation of callbackFn . Therefore:

• callbackFn will not visit any elements added beyond the array’s initial length when the call to find() began.
• Changes to already-visited indexes do not cause callbackFn to be invoked on them again.
• If an existing, yet-unvisited element of the array is changed by callbackFn , its value passed to the callbackFn will be the value at the time that element gets visited. Deleted elements are visited as if they were undefined .

Warning: Concurrent modifications of the kind described above frequently lead to hard-to-understand code and are generally to be avoided (except in special cases).

The find() method is generic. It only expects the this value to have a length property and integer-keyed properties.

Examples

Find an object in an array by one of its properties

const inventory = [  name: "apples", quantity: 2 >,  name: "bananas", quantity: 0 >,  name: "cherries", quantity: 5 >, ]; function isCherries(fruit)  return fruit.name === "cherries"; > console.log(inventory.find(isCherries)); // 

Using arrow function and destructuring

const inventory = [  name: "apples", quantity: 2 >,  name: "bananas", quantity: 0 >,  name: "cherries", quantity: 5 >, ]; const result = inventory.find(( name >) => name === "cherries"); console.log(result); // 

Find a prime number in an array

The following example finds an element in the array that is a prime number (or returns undefined if there is no prime number):

function isPrime(element, index, array)  let start = 2; while (start  Math.sqrt(element))  if (element % start++  1)  return false; > > return element > 1; > console.log([4, 6, 8, 12].find(isPrime)); // undefined, not found console.log([4, 5, 8, 12].find(isPrime)); // 5 

Using find() on sparse arrays

Empty slots in sparse arrays are visited, and are treated the same as undefined .

// Declare array with no elements at indexes 2, 3, and 4 const array = [0, 1, , , , 5, 6]; // Shows all indexes, not just those with assigned values array.find((value, index) =>  console.log("Visited index", index, "with value", value); >); // Visited index 0 with value 0 // Visited index 1 with value 1 // Visited index 2 with value undefined // Visited index 3 with value undefined // Visited index 4 with value undefined // Visited index 5 with value 5 // Visited index 6 with value 6 // Shows all indexes, including deleted array.find((value, index) =>  // Delete element 5 on first iteration if (index === 0)  console.log("Deleting array[5] with value", array[5]); delete array[5]; > // Element 5 is still visited even though deleted console.log("Visited index", index, "with value", value); >); // Deleting array[5] with value 5 // Visited index 0 with value 0 // Visited index 1 with value 1 // Visited index 2 with value undefined // Visited index 3 with value undefined // Visited index 4 with value undefined // Visited index 5 with value undefined // Visited index 6 with value 6 

Calling find() on non-array objects

The find() method reads the length property of this and then accesses each property whose key is a nonnegative integer less than length .

const arrayLike =  length: 3, "-1": 0.1, // ignored by find() since -1 < 00: 2, 1: 7.3, 2: 4, >; console.log(Array.prototype.find.call(arrayLike, (x) => !Number.isInteger(x))); // 7.3 

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Polyfill of Array.prototype.find in core-js
• Indexed collections
• Array
• Array.prototype.findIndex()
• Array.prototype.findLast()
• Array.prototype.findLastIndex()
• Array.prototype.includes()
• Array.prototype.filter()
• Array.prototype.every()
• Array.prototype.some()
• TypedArray.prototype.find()

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This page was last modified on Jun 27, 2023 by MDN contributors.

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