DEV Community: Ahmad Adibzad

Comparing JavaScript Array Methods: reverse() vs toReversed()

Ahmad Adibzad — Thu, 29 Feb 2024 19:56:12 +0000

The reverse() function in JavaScript is commonly used to reverse an array. However, there is a new function called the toReversed(), which may be more suitable depending on the situation. Your code might have unexpected results if you use reverse() without knowing its effects.

The main difference is that the reverse() function changes the original array. For example, we are going to reverse the following array using the reverse function:

reverse():

const arr = [1,2,3];
arr.reverse();
console.log(arr); // [3,2,1]

As you can see, the original array has mutated because the reverse() returns a reference to the original array. Now let's use the toReversed(). This function returns a copy of the original array and doesn't change it:

toReversed():

const arr = [1,2,3];
arr.toReversed();
console.log(arr); // [1,2,3]

The next difference we must know is that empty slots remain empty in the reverse() function, while in toReversed() empty slots become undefined.

reverse():

const arr = [1,2,3];
delete arr[0];
arr.reverse();
console.log(arr); // [3, 2, empty]

toReversed():

const arr = [1,2,3];
delete arr[0];
const arr2 = arr.toReversed();
console.log(arr2) // [3, 2, undefined]

Easy Ways to Compare Two Arrays in JavaScript

Ahmad Adibzad — Wed, 31 May 2023 20:23:52 +0000

Comparing two arrays is one of the widely used and most important challenges you might face in programming. There are many ways to do this, but we are going to learn the easiest and fastest ways.

1. Using loops

Of course, the first way would be looping. We can quickly compare array elements one by one. No matter whether it is a "while" loop or a for loop. First, we need to check the length of the two arrays. If both have the same size, we can keep the comparison up.

function compareTwoArrays(arr1, arr2) {
  if (arr1.length !== arr2.length)
    return false;

  for (let i = 0; i < arr1.length; i++) {
    if (arr1[i] !== arr2[i])
      return false;
  }

  return true;
}

compareTwoArrays([null, 1, 2], [undefined, 1, 2])

Now, let's test our function. We are going to pass two arrays that are different:

let array1 = [null, 1, 2];
let array2 = [undefined, 1, 2];

compareTwoArrays(array1, array2)  // false

As we expect, it returns false, because null is not equal to undefined

Then, let's pass two arrays that are exactly the same:

let array3 = [null, 1, "a"];
let array4 = [null, 1, "a"];

compareTwoArrays(array3, array4) // returns true

This time, it returns true.

2. Using every() method

What does the every() method do? The every() method executes a function for every array element. So we can use it instead of loops. The every() method returns a boolean, and we will return the result as the result of the function. If all the elements of two arrays are equal at the same index, it returns true, otherwise returns false.

function compareTwoArrays(arr1, arr2) {
  if (arr1.length !== arr2.length)
    return false;

  return arr1.every((element, index) => {
    return element === arr2[index]
  });
}

let array1 = [null, 1, "a"];
let array2 = [null, 1, "a"];
compareTwoArrays(array1 , array2); // true

And the result will be the same as before.

3 Ways to Reverse a String in JavaScript

Ahmad Adibzad — Fri, 31 Mar 2023 20:24:27 +0000

In this post, you’ll learn how to work with the string.split(), string.join() functions, and finally spread operator.

JavaScript is a fantastic programming language that allows us to write code differently. Reversing a string in JavaScript is simple. Assuming we have a string like “JavaScript forever” we want to reverse all the characters of that. Let’s get started to do it.

1. Using loops

In most programming languages, and for new developers, using loops is the first way they can do it. Since the string is an iterable type in JavaScript, you can iterate through each character from the last to the first.

const str = "JavaScript forever";
let reversed = "";

for (let i = str.length - 1; i >= 0; i - ) {
  reversed += str[i];
}

console.log(reversed); // reverof tpircSavaJ

2. Using the split and join functions

In this way, you need to convert the string to an array. In JavaScript, you can split string characters into an array by using the split() function.

const str = "A text";

const arr = str.split('');  // ['A', ' ', 't', 'e', 'x', 't']

const reversedArr = arr.reverse(); // ['t', 'x', 'e', 't', ' ', 'A']

const reversedStr = reversedArr.join(''); // txet A

console.log(reversedStr); // txet A

You can merge all the lines into one line:

const result = original.split('').reverse().join('');

3. Using the spread operator

Still looking for an advanced way? The spread operator (...) allows us to create a real copy of an iterable value and put it into an object or array. So here, the spread operator can be used instead of the split() function to make an array from the string:

const str = "A text";
const arr = [...str]; // Creates an array of string characters
const reversedArr = arr.reverse();
const reversedStr = reversedArr.join('');
console.log(reversedStr); // txet A

Of course, You can merge them all into one line:

const result = [...str].reverse().join('');