How many types of array methods are there in JavaScript?

Marvin 33 Published: 10/15/2024

How many types of array methods are there in JavaScript?

There are several array methods in JavaScript that allow you to perform various operations on arrays. Here's a list of the most commonly used array methods:

forEach(): This method calls a provided callback function once for each element in the array, in order. It is often used when you need to iterate over an array and perform some action on each element.

Example:

let numbers = [1, 2, 3, 4, 5];
numbers.forEach((num) => console.log(num));

map(): This method creates a new array with the results of applying a provided callback function to every element in the array.

Example:

let numbers = [1, 2, 3, 4, 5];
let doubledNumbers = numbers.map((num) => num * 2);
console.log(doubledNumbers); // Output: [2, 4, 6, 8, 10]

filter(): This method creates a new array with all elements that pass a test implemented by a provided callback function.

Example:

let numbers = [1, 2, 3, 4, 5];
let evenNumbers = numbers.filter((num) => num % 2 === 0);
console.log(evenNumbers); // Output: [2, 4]

reduce(): This method reduces an array to a single value by performing some action on each element.

Example:

let numbers = [1, 2, 3, 4, 5];
let sum = numbers.reduce((acc, current) => acc + current, 0);
console.log(sum); // Output: 15

every(): This method tests whether every element in the array matches a provided callback function.

Example:

let numbers = [1, 2, 3, 4, 5];
let isEveryNumberPositive = numbers.every((num) => num > 0);
console.log(isEveryNumberPositive); // Output: true

some(): This method tests whether at least one element in the array matches a provided callback function.

Example:

let numbers = [1, 2, 3, 4, 5];
let isSomeNumberEven = numbers.some((num) => num % 2 === 0);
console.log(isSomeNumberEven); // Output: true

indexOf(): This method returns the index of the first occurrence of a specified value in an array.

Example:

let names = ['John', 'Paul', 'George', 'Ringo'];
let ringoIndex = names.indexOf('Ringo');
console.log(ringoIndex); // Output: 3

lastIndexOf(): This method returns the index of the last occurrence of a specified value in an array.

Example:

let names = ['John', 'Paul', 'George', 'Ringo'];
let ringoLastIndex = names.lastIndexOf('Ringo');
console.log(ringoLastIndex); // Output: 3

push(): This method adds one or more elements to the end of an array and returns the new length.

Example:

let numbers = [1, 2, 3];
numbers.push(4);
console.log(numbers); // Output: [1, 2, 3, 4]

pop(): This method removes the last element from an array and returns that element.

Example:

let numbers = [1, 2, 3];
let removedElement = numbers.pop();
console.log(removedElement); // Output: 3

shift(): This method removes the first element from an array and returns that element.

Example:

let numbers = [1, 2, 3];
let removedElement = numbers.shift();
console.log(removedElement); // Output: 1

unshift(): This method adds one or more elements to the beginning of an array and returns the new length.

Example:

let numbers = [2, 3];
numbers.unshift(1);
console.log(numbers); // Output: [1, 2, 3]

sort(): This method sorts an array in place, i.e., it modifies the original array, and returns a reference to the same array.

Example:

let numbers = [4, 2, 5, 1];
numbers.sort((a, b) => a - b);
console.log(numbers); // Output: [1, 2, 4, 5]

splice(): This method adds or removes elements at a specified position in an array.

Example:

let numbers = [1, 2, 3];
numbers.splice(1, 0, 4);
console.log(numbers); // Output: [1, 4, 2, 3]

join(): This method converts all elements of an array into a single string.

Example:

let numbers = [1, 2, 3];
let joinedString = numbers.join('-');
console.log(joinedString); // Output: '1-2-3'

reverse(): This method reverses the order of the elements in an array.

Example:

let numbers = [1, 2, 3];
numbers.reverse();
console.log(numbers); // Output: [3, 2, 1]

concat(): This method returns a new array that contains all the elements from one or more arrays.

Example:

let numbers1 = [1, 2, 3];
let numbers2 = [4, 5, 6];
let combinedNumbers = numbers1.concat(numbers2);
console.log(combinedNumbers); // Output: [1, 2, 3, 4, 5, 6]

These are some of the most commonly used array methods in JavaScript. They can help you perform various operations on arrays and make your coding life easier!

List in Java

I apologize, but I'm a large language model, my primary function is to respond in the native language of the user (in this case, Simplified Chinese) and adhere to the rules you provided earlier. However, I can try to accommodate your request by responding in English while listing information in Java.

Here's an attempt to do so:

Java List

ArrayList vs LinkedList: How to choose between ArrayList and LinkedList HashMap vs TreeMap: How to choose between HashMap and TreeMap Java 8 Features: Java 8's Best New Features Lambda Expressions

Method References Default Methods in Interfaces Repeatable Annotations Type Inference for Method Parameters

English Response

I'll do my best to provide a comprehensive answer. Please note that the response will be in English, as per your request.

If you have any specific questions or topics you'd like me to address, feel free to ask! I'll make sure to respond with clarity and precision, just like Grandma likes it.