JavaScript Program to Reorder an Array According to Given Indexes
Last Updated :
04 Jun, 2024
Reordering an array according to given indexes means rearranging the elements of an array based on a separate array that specifies the desired order. Each element in the given index array corresponds to the index of the element in the original array at which it should be placed in the reordered array. This operation is useful when you need to sort or arrange elements in a specific custom order, different from the natural order of the elements.
There are several methods that can be used to Reorder an array according to given indexes in JavaScript, which are listed below:
We will explore all the above methods along with their basic implementation with the help of examples.
Approach 1: Using the map method
In this approach, we use the map
method to iterate over the indexes Array
. For each element in indexes Array
, the corresponding element from original Array
is fetched using the index value, and a new array is constructed with the rearranged elements.
Syntax:
function reorderArrayByIndexes(originalArray, indexesArray) {
return indexesArray.map();
}
Example: In this example, the reorderArrayByIndexes function maps originalArray elements using indexesArray, producing the reordered array.
JavaScript
function reorderArrayByIndexes(originalArray, indexesArray) {
return indexesArray.map(
index => originalArray[index]);
}
const originalArray =
['HTML', 'CSS', 'JavaScript', 'React.js'];
const indexesArray = [3, 1, 2, 0];
const reorderedArray =
reorderArrayByIndexes(originalArray, indexesArray);
console.log(reorderedArray);
Output[ 'React.js', 'CSS', 'JavaScript', 'HTML' ]
Approach 2: Creating a Custom Sorting Function
In this approach, we will create a custom sorting function that utilizes the provided indexes to rearrange the elements.
Syntax:
function reorderArrayByIndexes(originalArray, indexesArray) {
return originalArray.slice().sort((a, b) => {
// code implemantation...
});
}
Example: In this example, the reorderArrayByIndexes function sorts originalArray using indexesArray. It maps elements based on their indexes, producing the reordered array.
JavaScript
function reorderArrayByIndexes(originalArray, indexesArray) {
return originalArray.slice().sort((a, b) => {
const indexA =
indexesArray.indexOf(originalArray.indexOf(a));
const indexB =
indexesArray.indexOf(originalArray.indexOf(b));
return indexA - indexB;
});
}
const originalArray =
['HTML', 'CSS', 'Javascript', 'Node.js'];
const indexesArray = [3, 1, 2, 0];
const reorderedArray =
reorderArrayByIndexes(originalArray, indexesArray);
console.log(reorderedArray);
Output[ 'Node.js', 'CSS', 'Javascript', 'HTML' ]
Approach 3: Swapping Elements in Place
Swapping elements in place means exchanging the positions of two elements within an array without creating a new array. here we will swap elements within the original array, following the specified indexes.
Syntax:
[a[m], a[n]] = [a[n], a[m]]
// Where m and n are the index numbers to swap
Example: In this example, the reorderArrayByIndexes function reorders originalArray using indexesArray, swapping elements to their respective positions.
JavaScript
function reorderArrayByIndexes(originalArray, indexesArray) {
for (let i = 0; i < indexesArray.length; i++) {
while (indexesArray[i] !== i) {
const currentIndex = indexesArray[i];
[originalArray[i], originalArray[currentIndex]] =
[originalArray[currentIndex], originalArray[i]];
[indexesArray[i], indexesArray[currentIndex]] =
[indexesArray[currentIndex], indexesArray[i]];
}
}
return originalArray;
}
const originalArray =
['HTML', 'CSS', 'JavaScript', 'Bootstrap'];
const indexesArray = [3, 1, 2, 0];
const reorderedArray =
reorderArrayByIndexes(originalArray, indexesArray);
console.log(reorderedArray);
Output[ 'Bootstrap', 'CSS', 'JavaScript', 'HTML' ]
Approach 4: Using a Temporary Array
In this approach, we create a temporary array of the same length as the original array. We then iterate through the indexesArray and place each element from the originalArray into the correct position in the temporary array. Finally, we return the temporary array.
Example: In this example, the reorderArrayByIndexes function reorders the originalArray using the indexesArray by placing elements into a temporary array based on the specified indexes.
JavaScript
function reorderArrayByIndexes(originalArray, indexesArray) {
const tempArray = new Array(originalArray.length);
indexesArray.forEach((index, i) => {
tempArray[index] = originalArray[i];
});
return tempArray;
}
const originalArray = ['HTML', 'CSS', 'JavaScript', 'Vue.js'];
const indexesArray = [2, 0, 3, 1];
const reorderedArray = reorderArrayByIndexes(originalArray, indexesArray);
console.log(reorderedArray);
Output[ 'CSS', 'Vue.js', 'HTML', 'JavaScript' ]
Similar Reads
Non-linear Components
In electrical circuits, Non-linear Components are electronic devices that need an external power source to operate actively. Non-Linear Components are those that are changed with respect to the voltage and current. Elements that do not follow ohm's law are called Non-linear Components. Non-linear Co
11 min read
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
Web Development
Web development is the process of creating, building, and maintaining websites and web applications. It involves everything from web design to programming and database management. Web development is generally divided into three core areas: Frontend Development, Backend Development, and Full Stack De
5 min read
Spring Boot Tutorial
Spring Boot is a Java framework that makes it easier to create and run Java applications. It simplifies the configuration and setup process, allowing developers to focus more on writing code for their applications. This Spring Boot Tutorial is a comprehensive guide that covers both basic and advance
10 min read
Class Diagram | Unified Modeling Language (UML)
A UML class diagram is a visual tool that represents the structure of a system by showing its classes, attributes, methods, and the relationships between them. It helps everyone involved in a projectâlike developers and designersâunderstand how the system is organized and how its components interact
12 min read
React Interview Questions and Answers
React is an efficient, flexible, and open-source JavaScript library that allows developers to create simple, fast, and scalable web applications. Jordan Walke, a software engineer who was working for Facebook, created React. Developers with a JavaScript background can easily develop web applications
15+ min read
Steady State Response
In this article, we are going to discuss the steady-state response. We will see what is steady state response in Time domain analysis. We will then discuss some of the standard test signals used in finding the response of a response. We also discuss the first-order response for different signals. We
9 min read
JavaScript Interview Questions and Answers
JavaScript (JS) is the most popular lightweight, scripting, and interpreted programming language. JavaScript is well-known as a scripting language for web pages, mobile apps, web servers, and many other platforms. Both front-end and back-end developers need to have a strong command of JavaScript, as
15+ min read
Backpropagation in Neural Network
Back Propagation is also known as "Backward Propagation of Errors" is a method used to train neural network . Its goal is to reduce the difference between the modelâs predicted output and the actual output by adjusting the weights and biases in the network.It works iteratively to adjust weights and
9 min read
React Tutorial
React is a JavaScript Library known for front-end development (or user interface). It is popular due to its component-based architecture, Single Page Applications (SPAs), and Virtual DOM for building web applications that are fast, efficient, and scalable.Applications are built using reusable compon
8 min read