Copy an Array in JavaScript - onlinecode

Copy an Array in JavaScript – onlinecode

Copy an Array in JavaScript

In this post, we will give you information about Copy an Array in JavaScript. Here we will give you detail about Copy an Array in JavaScript And how to use it also give you a demo for it if it is necessary.

There are several easy ways to clone an array in JavaScript. You can use the Array#slice() method, or the spread operator.

const arr = ['hello', 'world'];

// Clone using 'slice()'
const arr2 = arr.slice();
arr2; // ['hello', 'world']
arr2 === arr; // false

// Clone using spread operator '...'
const arr3 = [...arr];
arr2; // ['hello', 'world']
arr2 === arr; // false

Two other common approaches are by concat()-ing the array to an empty array and by using the map() method:

// Clone using 'concat()'
const arr4 = [].concat(arr);
arr4; // ['hello', 'world']
arr4 === arr; // false

// Clone using 'map()'
const arr5 = => v);
arr5; // ['hello', 'world']
arr5 === arr; // false

These 4 approaches for copying an array are effectively identical and there isn’t much reason to prefer one over
the other. The most significant difference is that slice() enjoys slightly better browser support – all the
way back to Internet Explorer 4.

Deep Copy vs Shallow Copy for Copy an Array in JavaScript

Keep in mind that all 4 of the above approaches create a shallow clone of the
array. In other words, they clone the array itself, but not the array elements.

This difference doesn’t matter when you have an array of primitives (numbers, strings, null, undefined), but
it does when you have an array of objects.

const arr = [{ answer: 42 }];

const arr2 = arr.slice();
arr2[0].answer = 0;

// '0', because 'arr[0]' is a reference to the same object as 'arr2[0]'

JavaScript doesn’t have a built-in approach for deep cloning an array. You would need to use a library that
has a cloneDeep() function, like lodash.

const arr = [{ answer: 42 }];

const arr2 = require('lodash').cloneDeep(arr);
arr2[0].answer = 0;

// '42', because Lodash did a deep clone.

JavaScript Fundamentals for Copy an Array in JavaScript

JavaScript is a programming language that is used to create interactive web pages. It is a client-side scripting language, which means that it runs on the user’s browser. JavaScript can be used to add animation, interactivity, and functionality to web pages.

Here are some of the fundamentals of JavaScript:

  • Variables: Variables are used to store data. They are declared using the var keyword.
  • Data types: JavaScript has a variety of data types, including strings, numbers, booleans, objects, and arrays.
  • Operators: Operators are used to perform operations on data.
  • Control flow statements: Control flow statements allow you to control the order in which your code is executed.
  • Functions: Functions are blocks of code that can be reused.
  • Objects: Objects are used to store data in key-value pairs.
  • Arrays: Arrays are used to store data in a sequential order.
  • Events and event handlers: Events are notifications that are sent by the browser when something happens, such as when the user clicks on an element or moves the mouse over an element. Event handlers are functions that are called in response to an event.
  • DOM manipulation: The Document Object Model (DOM) is a tree-like structure that represents the elements of a web page. JavaScript can be used to manipulate the DOM to change the appearance or behavior of a web page.

These are just some of the fundamentals of JavaScript. There are many other concepts that you can learn as you continue to develop your skills.

Here are some resources that you can use to learn more about JavaScript:

  • Mozilla Developer Network (MDN): The MDN is a great resource for learning about JavaScript. It has a comprehensive reference guide, tutorials, and articles on a wide range of topics.
  • W3Schools: W3Schools is another great resource for learning about JavaScript. It has interactive tutorials and quizzes that can help you learn the basics of the language.
  • is a website that provides in-depth tutorials on JavaScript. It also has a forum where you can ask questions and get help from other JavaScript developers.

I hope this helps!

Here are some additional tips for learning JavaScript:

  • Start with the basics: Before you start trying to build complex applications, it’s important to learn the basics of JavaScript. This includes things like variables, data types, operators, and control flow statements.
  • Practice regularly: The best way to learn JavaScript is to practice regularly. Try to find some time each day to work on JavaScript projects.
  • Get help from others: If you get stuck, don’t be afraid to ask for help from others. There are many online forums and communities where you can get help from other JavaScript developers.

With a little practice, you’ll be able to learn JavaScript and start building amazing web applications.

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