Conditionally add an extra element while pushing multi-element rows into a 2d array in a loop

2 min read 07-10-2024

Conditionally add an extra element while pushing multi-element rows into a 2d array in a loop

Dynamic Array Building: Adding Elements Conditionally in Loops

Imagine you're building a table with rows of data, but some rows require an extra column. You'd want to dynamically add this column only when necessary, without cluttering your code with unnecessary conditional checks. This is a common scenario in programming, and it's where the concept of conditionally adding elements while pushing multi-element rows into a 2D array comes into play.

The Problem and Its Rephrasing

The Problem: Let's say you have a dataset with information about books. Each book has a title, author, and sometimes a genre. You want to store this data in a 2D array, where each row represents a book and each column represents a piece of information. However, you don't want to have a dedicated "genre" column for every book since not all books have a genre specified.

Simplified: You want to create a table-like structure (2D array) where each row represents a book, and the columns are title, author, and optionally genre.

Original Code (Illustrative Example):

const books = [
  { title: "Book 1", author: "Author A", genre: "Fiction" },
  { title: "Book 2", author: "Author B" },
  { title: "Book 3", author: "Author C", genre: "Non-Fiction" }
];

const bookArray = [];

for (let i = 0; i < books.length; i++) {
  const book = books[i];
  bookArray.push([book.title, book.author]); // Assuming all books have title and author
  if (book.genre) { // If genre is available, add it as an extra column
    bookArray[i].push(book.genre);
  }
}

console.log(bookArray);

Insights and Analysis

This example showcases the core challenge:

Dynamic Row Structure: The number of columns in each row might vary depending on the presence of a specific element (genre in this case).
Efficiency: Directly checking for the presence of the 'genre' property in every iteration is an effective way to handle the dynamic structure, but it might not be the most efficient approach for large datasets.

Optimizing the Approach

Here's a refined approach that offers improved readability and potential performance benefits:

const books = [
  { title: "Book 1", author: "Author A", genre: "Fiction" },
  { title: "Book 2", author: "Author B" },
  { title: "Book 3", author: "Author C", genre: "Non-Fiction" }
];

const bookArray = [];

for (let i = 0; i < books.length; i++) {
  const book = books[i];
  const row = [book.title, book.author];
  if (book.genre) { 
    row.push(book.genre);
  }
  bookArray.push(row); 
}

console.log(bookArray);

Explanation:

We introduce a temporary row array to hold the elements for each book.
We conditionally add the genre to the row array if it exists.
Finally, we push the complete row into the bookArray.

This approach eliminates the need to access bookArray[i] repeatedly, potentially improving performance for large datasets.

Conclusion

This scenario is a classic example of how we can tailor our code to handle dynamic data structures efficiently. By utilizing conditional logic, temporary variables, and efficient array manipulation, we can ensure that our 2D array reflects the varying structure of our data while maintaining clean and readable code.