To help you perform common tasks efficiently, JavaScript provides a wide variety of array methods. These methods allow you to add, remove, find, and transform array elements with ease.
Learn More on JavaScript Array
1. JavaScript Array length
The length property of an array returns the number of elements in the array. It automatically updates as elements are added or removed.
JavaScript
let a = ["HTML", "CSS", "JS", "React"];
console.log(a.length);
In this example
- The code defines an array 'a' containing the elements "HTML", "CSS", "JS", and "React".
- a.length returns the number of elements in the array.
2. JavaScript Array toString() Method
The toString() method converts the given value into the string with each element separated by commas.
JavaScript
let a = ["HTML", "CSS", "JS", "React"];
let s = a.toString();
console.log(s);
In this example
- The code defines an array "a" containing the elements "HTML", "CSS", "JS", and "React".
- The toString() method converts the array 'a' into a string.
3. JavaScript Array join() Method
This join() method creates and returns a new string by concatenating all elements of an array. It uses a specified separator between each element in the resulting string.
JavaScript
let a = ["HTML", "CSS", "JS", "React"];
console.log(a.join('|'));
In this example
- The code defines an array 'a' with the elements "HTML", "CSS", "JS", and "React".
- The join('|') method combines the array elements into a single string, with each element separated by a pipe (|) character.
4. JavaScript Array delete Operator
The delete operator is used to delete the given value which can be an object, array, or anything.
JavaScript
let emp = {
firstName: "Riya",
lastName: "Kaur",
salary: 40000
}
console.log(delete emp.salary);
console.log(emp);
Outputtrue
{ firstName: 'Riya', lastName: 'Kaur' }
In this example
- The delete emp.salary statement removes the salary property from the emp object and returns true if successful.
- After deletion, console.log(emp) prints the updated object without the salary property.
5. JavaScript Array concat() Method
The concat() method is used to concatenate two or more arrays and it gives the merged array.
JavaScript
let a1 = [11, 12, 13];
let a2 = [14, 15, 16];
let a3 = [17, 18, 19];
let newArr = a1.concat(a2, a3);
console.log(newArr);
Output[
11, 12, 13, 14, 15,
16, 17, 18, 19
]
In this example
- The code defines three arrays, a1, a2, and a3, and uses the concat() method to merge them into a single array newArr.
- The resulting array [11, 12, 13, 14, 15, 16, 17, 18, 19] is logged to the console, preserving the order of elements from the original arrays.
6. JavaScript Array flat() Method
The flat() method is used to flatten the array i.e. it merges all the given array and reduces all the nesting present in it.
JavaScript
const a1 = [['1', '2'], ['3', '4', '5',['6'], '7']];
const a2 = a1.flat(Infinity);
console.log(a2);
Output[
'1', '2', '3',
'4', '5', '6',
'7'
]
In this example
- The code defines a multilevel (nested) array 'a1' and uses the flat(Infinity) method to flatten it completely into a single-level array.
7. JavaScript Array.push() Method
The push() method is used to add an element at the end of an Array. As arrays in JavaScript are mutable objects, we can easily add or remove elements from the Array.
JavaScript
let a = [10, 20, 30, 40, 50];
a.push(60);
a.push(70, 80, 90);
console.log(a);
Output[
10, 20, 30, 40, 50,
60, 70, 80, 90
]
8. JavaScript Array.unshift() Method
The unshift() method is used to add elements to the front of an Array.
JavaScript
let a = [20, 30, 40];
a.unshift(10, 20);
console.log(a);
Output[ 10, 20, 20, 30, 40 ]
9. JavaScript Array.pop() Method
The pop() method is used to remove elements from the end of an array.
JavaScript
let a = [20, 30, 40, 50];
a.pop();
console.log(a);
10. JavaScript Array.shift() Method
The shift() method is used to remove elements from the beginning of an array
JavaScript
let a = [20, 30, 40, 50];
a.shift();
console.log(a);
11. JavaScript Array.splice() Method
The splice() method is used to Insert and Remove elements in between the Array.
JavaScript
let a = [20, 30, 40, 50];
a.splice(1, 3);
a.splice(1, 0, 3, 4, 5);
console.log(a);
- The first a.splice(1, 3) removes 3 elements (30, 40, 50) starting at index 1. The array becomes [20].
- The second a.splice(1, 0, 3, 4, 5) inserts 3, 4, and 5 at index 1 without removing anything. The array becomes [20, 3, 4, 5].
12. JavaScript Array.slice() Method
The slice() method returns a new array containing a portion of the original array, based on the start and end index provided as arguments
JavaScript
const a = [1, 2, 3, 4, 5];
const res = a.slice(1, 4);
console.log(res);
console.log(a)
Output[ 2, 3, 4 ]
[ 1, 2, 3, 4, 5 ]
In this example
- The slice() method creates a new array by extracting elements from index 1 to 3 (exclusive of 4) from the original array.
- The original array remains unchanged, and the result is [2, 3, 4].
13. JavaScript Array some() Method
The some() method checks whether at least one of the elements of the array satisfies the condition checked by the argument function.
JavaScript
const a = [1, 2, 3, 4, 5];
let res = a.some((val) => val > 4);
console.log(res);
In this example
- The some() method checks if at least one element in the array satisfies the provided condition.
- (val) => val > 4: The condition checks if any element in the array is greater than 4.
- The method stops as soon as it finds the first matching element, making it efficient for large arrays.
14. JavaScript Array map() Method
The map() method creates an array by calling a specific function on each element present in the parent array. It is a non-mutating method.
JavaScript
let a = [4, 9, 16, 25];
let sub = a.map(geeks);
function geeks() {
return a.map(Math.sqrt);
}
console.log(sub);
Output[ [ 2, 3, 4, 5 ], [ 2, 3, 4, 5 ], [ 2, 3, 4, 5 ], [ 2, 3, 4, 5 ] ]
In this example
- The code defines a geeks function, but instead of operating on the individual array 'a' elements, it applies Math.sqrt() to the entire a array, resulting in a nested array of square roots.
- The output will be an array of the same length as a, but each element will be the result of applying arr.map(Math.sqrt).
15. JavaScript Array filter() method
The filter() method in JavaScript creates a new array with all elements that pass the test implemented by the provided function. It does not modify the original array.
JavaScript
let a1 = [1, 2, 3, 4, 5]
let a2 = a1.filter((num) => num > 1)
console.log(a2)
In this example
- The filter() method is used to create a new array (a2) that contains all elements of the original array that satisfy the condition (num > 1).
- The filter() method does not modify the original array. It returns a new array, leaving the original one unchanged.
16. JavaScript Array reduce() Method
The reduce() method is used to reduce the array to a single value and executes a provided function for each value of the array (from left to right) and the return value of the function is stored in an accumulator.
JavaScript
let a = [88, 50, 25, 10];
let sub = a.reduce(geeks);
function geeks(tot, num) {
return tot - num;
}
console.log(sub);
In this example
- The reduce() method iterates over the array 'a' and applies the geeks function, which subtracts each element (num) from the running total (tot).
- For the array [88, 50, 25, 10], the calculation proceeds as: 88 - 50 - 25 - 10.
17. JavaScript Array reverse() method
The reverse() method is used to reverse the order of elements in an array. It modifies the array in place and returns a reference to the same array with the reversed order.
JavaScript
let a = [1, 2, 3, 4, 5];
a.reverse();
console.log(a);
In this example
- The reverse() method reverses the order of elements in the array arr in place, modifying the original array.
- After applying reverse(), the array.
18. JavaScript Array values() method
The values() method returns a new Array Iterator object that contains the values for each index in the array.
JavaScript
const a = ["Apple", "Banana", "Cherry"];
const res = a.values();
for (const value of res) {
console.log(value);
}
OutputApple
Banana
Cherry
In this example
- The values() method returns an iterator object that allows iterating over the values of the 'a' array.
- The for...of loop is used to iterate over the iterator and log each fruit ("Apple", "Banana", "Cherry") to the console.
JavaScript Array Complete Reference
We have created a complete list of array methods, please check this article JavaScript Array Complete Reference for more details.
Note: All the above examples can be tested by typing them within the script tag of HTML or directly into the browser's console.
Learn JavaScript from beginners to advanced with JavaScript Tutorial
Similar Reads
JavaScript Tutorial JavaScript is a programming language used to create dynamic content for websites. It is a lightweight, cross-platform, and single-threaded programming language. It's an interpreted language that executes code line by line, providing more flexibility.JavaScript on Client Side: On the client side, Jav
11 min read
JavaScript Basics
Introduction to JavaScriptJavaScript is a versatile, dynamically typed programming language used for interactive web applications, supporting both client-side and server-side development, and integrating seamlessly with HTML, CSS, and a rich standard library.JavaScript is a single-threaded language that executes one task at
7 min read
JavaScript VersionsJavaScript is a popular programming language used by developers all over the world. It’s a lightweight and easy-to-learn language that can run on both the client-side (in your browser) and the server-side (on the server). JavaScript was created in 1995 by Brendan Eich.In 1997, JavaScript became a st
2 min read
How to Add JavaScript in HTML Document?To add JavaScript in HTML document, several methods can be used. These methods include embedding JavaScript directly within the HTML file or linking an external JavaScript file.Inline JavaScriptYou can write JavaScript code directly inside the HTML element using the onclick, onmouseover, or other ev
3 min read
JavaScript SyntaxJavaScript syntax refers to the rules and conventions dictating how code is structured and arranged within the JavaScript programming language. This includes statements, expressions, variables, functions, operators, and control flow constructs.Syntaxconsole.log("Basic Print method in JavaScript");Ja
6 min read
JavaScript OutputJavaScript provides different methods to display output, such as console.log(), alert(), document.write(), and manipulating HTML elements directly. Each method has its specific use cases, whether for debugging, user notifications, or dynamically updating web content. Here we will explore various Jav
4 min read
JavaScript CommentsComments help explain code (they are not executed and hence do not have any logic implementation). We can also use them to temporarily disable parts of your code.1. Single Line CommentsA single-line comment in JavaScript is denoted by two forward slashes (//), JavaScript// A single line comment cons
2 min read
JS Variables & Datatypes
Variables and Datatypes in JavaScriptVariables and data types are foundational concepts in programming, serving as the building blocks for storing and manipulating information within a program. In JavaScript, getting a good grasp of these concepts is important for writing code that works well and is easy to understand.VariablesA variab
3 min read
Global and Local variables in JavaScriptIn JavaScript, understanding the difference between global and local variables is important for writing clean, maintainable, and error-free code. Variables can be declared with different scopes, affecting where and how they can be accessed. Global VariablesGlobal variables in JavaScript are those de
4 min read
JavaScript LetThe let keyword is a modern way to declare variables in JavaScript and was introduced in ECMAScript 6 (ES6). Unlike var, let provides block-level scoping. This behaviour helps developers avoid unintended issues caused by variable hoisting and scope leakage that are common with var.Syntaxlet variable
6 min read
JavaScript constThe const keyword in JavaScript is a modern way to declare variables, introduced in (ES6). It is used to declare variables whose values need to remain constant throughout the lifetime of the application.const is block-scoped, similar to let, and is useful for ensuring immutability in your code. Unli
5 min read
JavaScript Var StatementThe var keyword is used to declare variables in JavaScript. It has been part of the language since its inception. When a variable is declared using var, it is function-scoped or globally-scoped, depending on where it is declared.Syntaxvar variable = value;It declares a variable using var, assigns it
7 min read
JS Operators
JavaScript OperatorsJavaScript operators are symbols or keywords used to perform operations on values and variables. They are the building blocks of JavaScript expressions and can manipulate data in various ways.JavaScript OperatorsThere are various operators supported by JavaScript.1. JavaScript Arithmetic OperatorsAr
5 min read
Operator precedence in JavaScriptOperator precedence refers to the priority given to operators while parsing a statement that has more than one operator performing operations in it. Operators with higher priorities are resolved first. But as one goes down the list, the priority decreases and hence their resolution. ( * ) and ( / )
2 min read
JavaScript Arithmetic OperatorsJavaScript Arithmetic Operators are the operator that operate upon the numerical values and return a numerical value. Addition (+) OperatorThe addition operator takes two numerical operands and gives their numerical sum. It also concatenates two strings or numbers.JavaScript// Number + Number =>
6 min read
JavaScript Assignment OperatorsAssignment operators are used to assign values to variables in JavaScript.JavaScript// Lets take some variables x = 10 y = 20 x = y ; console.log(x); console.log(y); Output20 20 More Assignment OperatorsThere are so many assignment operators as shown in the table with the description.OPERATOR NAMESH
5 min read
JavaScript Comparison OperatorsJavaScript comparison operators are essential tools for checking conditions and making decisions in your code. 1. Equality Operator (==) The Equality operator is used to compare the equality of two operands. JavaScript// Illustration of (==) operator let x = 5; let y = '5'; // Checking of operands c
5 min read
JavaScript Logical OperatorsLogical operators in JavaScript are used to perform logical operations on values and return either true or false. These operators are commonly used in decision-making statements like if or while loops to control the flow of execution based on conditions.In JavaScript, there are basically three types
5 min read
JavaScript Bitwise OperatorsIn JavaScript, a number is stored as a 64-bit floating-point number but bitwise operations are performed on a 32-bit binary number. To perform a bit-operation, JavaScript converts the number into a 32-bit binary number (signed) and performs the operation and converts back the result to a 64-bit numb
5 min read
JavaScript Ternary OperatorThe Ternary Operator in JavaScript is a shortcut for writing simple if-else statements. It’s also known as the Conditional Operator because it works based on a condition. The ternary operator allows you to quickly decide between two values depending on whether a condition is true or false.Syntax:con
5 min read
JavaScript Comma OperatorJavaScript Comma Operator mainly evaluates its operands from left to right sequentially and returns the value of the rightmost operand. JavaScriptlet x = (1, 2, 3); console.log(x); Output3 Here is another example to show that all expressions are actually executed.JavaScriptlet a = 1, b = 2, c = 3; l
2 min read
JavaScript Unary OperatorsJavaScript Unary Operators work on a single operand and perform various operations, like incrementing/decrementing, evaluating data type, negation of a value, etc.Unary Plus (+) OperatorThe unary plus (+) converts an operand into a number, if possible. It is commonly used to ensure numerical operati
4 min read
JavaScript in and instanceof operatorsJavaScript Relational Operators are used to compare their operands and determine the relationship between them. They return a Boolean value (true or false) based on the comparison result.JavaScript in OperatorThe in-operator in JavaScript checks if a specified property exists in an object or if an e
3 min read
JavaScript String OperatorsJavaScript String Operators are used to manipulate and perform operations on strings. There are two operators which are used to modify strings in JavaScript. These operators help us to join one string to another string.1. Concatenate OperatorConcatenate Operator in JavaScript combines strings using
3 min read
JS Statements
JavaScript StatementsJavaScript statements are programming instructions that a computer executes. A computer program is essentially a list of these "instructions" designed to perform tasks. In a programming language, such instructions are called statements.Types of Statements1. Variable Declarations (var, let, const)In
4 min read
JavaScript if-elseJavaScript if-else statement executes a block of code based on a condition. If the condition evaluates to true, the code inside the "if" block executes; otherwise, the code inside the "else" block, if present, executes. Such control statements are used to cause the flow of execution to advance and b
4 min read
JavaScript switch StatementThe JavaScript switch statement evaluates an expression and executes a block of code based on matching cases. It provides an alternative to long if-else chains, improving readability and maintainability, especially when handling multiple conditional branches.Switch Statement Example: Here, we will p
5 min read
JavaScript Break StatementJavaScript break statement is used to terminate the execution of the loop or the switch statement when the condition is true.In Switch Block (To come out of the block)JavaScriptconst fruit = "Mango"; switch (fruit) { case "Apple": console.log("Apple is healthy."); break; case "Mango": console.log("M
2 min read
JavaScript Continue StatementThe continue statement in JavaScript is used to break the iteration of the loop and follow with the next iteration. Example of continue to print only odd Numbers smaller than 10JavaScriptfor (let i = 0; i < 10; i++) { if (i % 2 == 0) continue; console.log(i); }Output1 3 5 7 9 How Does Continue Wo
1 min read
JavaScript Return StatementThe return statement in JavaScript is used to end the execution of a function and return a value to the caller. It is used to control function behaviour and optimise code execution.Syntaxreturn [expression]Expression Evaluation: The expression inside the brackets is evaluated and returned to the cal
4 min read
JS Loops
JavaScript LoopsLoops in JavaScript are used to reduce repetitive tasks by repeatedly executing a block of code as long as a specified condition is true. This makes code more concise and efficient.Suppose we want to print 'Hello World' five times. Instead of manually writing the print statement repeatedly, we can u
3 min read
JavaScript For LoopJavaScript for loop is a control flow statement that allows code to be executed repeatedly based on a condition. It consists of three parts: initialization, condition, and increment/decrement. javascript// for loop begins when x=2 // and runs till x <= 4 for (let x = 2; x <= 4; x++) { console.
5 min read
JavaScript While LoopThe while loop executes a block of code as long as a specified condition is true. In JavaScript, this loop evaluates the condition before each iteration and continues running as long as the condition remains trueHere's an example that prints from 1 to 5. JavaScriptlet count = 1; while (count <= 5
3 min read
JavaScript For In LoopThe JavaScript for...in loop iterates over the properties of an object. It allows you to access each key or property name of an object.JavaScriptconst car = { make: "Toyota", model: "Corolla", year: 2020 }; for (let key in car) { console.log(`${key}: ${car[key]}`); }Outputmake: Toyota model: Corolla
3 min read
JavaScript for...of LoopThe JavaScript for...of loop is a modern, iteration statement introduced in ECMAScript 2015 (ES6). Works for iterable objects such as arrays, strings, maps, sets, and more. It is better choice for traversing items of iterables compared to traditional for and for in loops, especially when we have bre
3 min read
JavaScript do...while LoopA do...while loop in JavaScript is a control structure where the code executes repeatedly based on a given boolean condition. It's similar to a repeating if statement. One key difference is that a do...while loop guarantees that the code block will execute at least once, regardless of whether the co
4 min read
JS Perfomance & Debugging
JS Object
Objects in JavascriptAn object in JavaScript is a data structure used to store related data collections. It stores data as key-value pairs, where each key is a unique identifier for the associated value. Objects are dynamic, which means the properties can be added, modified, or deleted at runtime.There are two primary w
4 min read
Introduction to Object Oriented Programming in JavaScriptAs JavaScript is widely used in Web Development, in this article we will explore some of the Object Oriented mechanisms supported by JavaScript to get the most out of it. Some of the common interview questions in JavaScript on OOPS include: How is Object-Oriented Programming implemented in JavaScrip
7 min read
JavaScript ObjectsIn our previous article on Introduction to Object Oriented Programming in JavaScript we have seen all the common OOP terminology and got to know how they do or don't exist in JavaScript. In this article, objects are discussed in detail.Creating Objects:In JavaScript, Objects can be created using two
6 min read
Creating objects in JavaScriptAn object in JavaScript is a collection of key-value pairs, where keys are strings (properties) and values can be any data type. Objects can be created using object literals, constructors, or classes. Properties are defined with key-value pairs, and methods are functions defined within the object, e
5 min read
JavaScript JSON ObjectsJSON (JavaScript Object Notation) is a handy way to share data. It's easy for both people and computers to understand. In JavaScript, JSON helps organize data into simple objects. Let's explore how JSON works and why it's so useful for exchanging information.const jsonData = { "key1" : "value1", ...
3 min read
JavaScript Object ReferenceJavaScript Objects are the most important data type and form the building blocks for modern JavaScript. The "Object" class represents the JavaScript data types. Objects are quite different from JavaScript’s primitive data types (Number, String, Boolean, null, undefined, and symbol). It is used to st
4 min read
JS Function
Functions in JavaScriptFunctions in JavaScript are reusable blocks of code designed to perform specific tasks. They allow you to organize, reuse, and modularize code. It can take inputs, perform actions, and return outputs.JavaScriptfunction sum(x, y) { return x + y; } console.log(sum(6, 9));Output15 Function Syntax and W
5 min read
How to write a function in JavaScript ?JavaScript functions serve as reusable blocks of code that can be called from anywhere within your application. They eliminate the need to repeat the same code, promoting code reusability and modularity. By breaking down a large program into smaller, manageable functions, programmers can enhance cod
4 min read
JavaScript Function CallThe call() method is a predefined JavaScript method. It can be used to invoke (call) a method with an owner object as an argument (parameter). This allows borrowing methods from other objects, executing them within a different context, overriding the default value, and passing arguments. Syntax: cal
2 min read
Different ways of writing functions in JavaScriptA JavaScript function is a block of code designed to perform a specific task. Functions are only executed when they are called (or "invoked"). JavaScript provides different ways to define functions, each with its own syntax and use case.Below are the ways of writing functions in JavaScript:Table of
3 min read
Difference between Methods and Functions in JavaScriptGrasping the difference between methods and functions in JavaScript is essential for developers at all levels. While both are fundamental to writing effective code, they serve different purposes and are used in various contexts. This article breaks down the key distinctions between methods and funct
3 min read
Explain the Different Function States in JavaScriptIn JavaScript, we can create functions in many different ways according to the need for the specific operation. For example, sometimes we need asynchronous functions or synchronous functions. Â In this article, we will discuss the difference between the function Person( ) { }, let person = Person ( )
3 min read
JavaScript Function Complete ReferenceA JavaScript function is a set of statements that takes inputs, performs specific computations, and produces outputs. Essentially, a function performs tasks or computations and then returns the result to the user.Syntax:function functionName(Parameter1, Parameter2, ..) { // Function body}Example: Be
3 min read
JS Array
JavaScript ArraysIn JavaScript, an array is an ordered list of values. Each value is called an element, and each element has a numeric position in the array, known as its index. Arrays in JavaScript are zero-indexed, meaning the first element is at index 0, the second at index 1, and so on.Array in JavaScriptWhy Use
7 min read
JavaScript Array MethodsTo help you perform common tasks efficiently, JavaScript provides a wide variety of array methods. These methods allow you to add, remove, find, and transform array elements with ease.Learn More on JavaScript ArrayTable of Content1. JavaScript Array length 2. JavaScript Array toString() Method3. Jav
8 min read
Best-Known JavaScript Array MethodsAn array is a special variable in all programming languages used to store multiple elements. JavaScript array come with built-in methods that every developer should know how to use. These methods help in adding, removing, iterating, or manipulating data as per requirements.There are some Basic JavaS
6 min read
Important Array Methods of JavaScriptJavaScript arrays are powerful tools for managing collections of data. They come with a wide range of built-in methods that allow developers to manipulate, transform, and interact with array elements.Some of the most important array methods in JavaScript areTable of Content1. JavaScript push() Metho
7 min read
JavaScript Array ReferenceJavaScript Array is used to store multiple elements in a single variable. It can hold various data types, including numbers, strings, objects, and even other arrays. It is often used when we want to store a list of elements and access them by a single variable.Syntax:const arr = ["Item1", "Item2", "
4 min read