Lesson 3

Hello there! Are you ready to enhance your **JavaScript** programming skills with another exciting exercise? In this unit, we will delve into the world of **matrices**. More specifically, we'll be transposing a given matrix. Let's dive into this matrix manipulation exercise without delay!

To begin, let's elaborate on the task at hand: we will write a JavaScript function named `transformMatrix()`

. This function will accept a 2D array (which represents a matrix) containing integers as input. Your goal is to return another 2D array, which is the transposed version of the given matrix.

When we mention 'transposing a matrix,' we are referring to the process of switching its rows and columns. In other words, all the rows of the original matrix should become columns in the transposed matrix, and vice versa.

For instance, if the original matrix (input 2D array) is:

JavaScript`1let matrix = [ 2 [1, 2, 3], 3 [4, 5, 6] 4];`

Then the transposed matrix (output 2D array) will be:

JavaScript`1let transposed = [ 2 [1, 4], 3 [2, 5], 4 [3, 6] 5];`

It is vital that your result maintains the integrity of the data types present in the original matrix. In simpler terms, the values in the input matrix are integers, and they should remain integers in the output matrix as well.

The initial step in building our solution involves determining the dimensions of the matrix. We need to know the number of rows and columns present in it. In JavaScript, the array length properties can provide this information. The number of rows is simply the length of the outer array, and the number of columns is the length of any of the inner arrays. It is important to note the inner arrays must all have the same length for the 2D array to be a proper matrix (and to allow for transposition).

JavaScript`1function transformMatrix(matrix) { 2 let rows = matrix.length; 3 let cols = rows > 0 ? matrix[0].length : 0; 4 // If rows > 0, the above line sets cols to 5 // the length of the first row, else sets to 0 6}`

The subsequent step is to create a "placeholder" for the transposed matrix that aligns with its required dimensions. This will be a new 2D array, but with the number of rows and columns swapped.

JavaScript`1function transformMatrix(matrix) { 2 let rows = matrix.length; 3 let cols = rows > 0 ? matrix[0].length : 0; 4 let result = []; 5 6 for (let i = 0; i < cols; ++i) { 7 result[i] = []; 8 } 9}`

In this code snippet, we create a new array object and populate it with empty arrays, one row for each column.

It's time to get to the crux of the matter — transposing the matrix. For every element in the original matrix, we want to move it from the `i`

th row and `j`

th column to the `j`

th row and `i`

th column of the transposed matrix.

JavaScript`1function transformMatrix(matrix) { 2 let rows = matrix.length; 3 let cols = rows > 0 ? matrix[0].length : 0; 4 let result = []; 5 6 for (let i = 0; i < cols; ++i) { 7 result[i] = []; 8 for (let j = 0; j < rows; ++j) { 9 result[i][j] = matrix[j][i]; 10 } 11 } 12 return result; 13} 14 15let matrix = [ 16 [1, 2, 3], 17 [4, 5, 6] 18]; 19 20let transposed = transformMatrix(matrix); 21 22for (let row of transposed) { 23 console.log(row.join(' ')); 24} 25 26// Outputs: 27// 1 4 28// 2 5 29// 3 6`

A straightforward nested `for`

loop can effortlessly execute this swap for all elements of the matrix: immediately after we create the new row, we populate it with the values using another `for`

loop, one column for each row in the original matrix.

Finally, we loop through each row in the transposed matrix using the `for`

loop `for (let row of transposed)`

. In each iteration, the `row`

variable holds one of the rows from the transposed matrix. Printing each `row`

outputs the entire transposed matrix, as expected.

This step concludes our solution!

With this, we've brought this lesson to a close! Congratulations on successfully implementing a function that can transpose matrices! This task is not simple, but by accomplishing it, you've demonstrated your understanding and proficiency in **JavaScript** multidimensional arrays, for-loops, and the concept of matrix transposition.

Your hard work continues, though. Now that you have acquired this valuable skill, it's time to reinforce it with more practice. During the next session, you will encounter practice problems that build on this concept. So, get ready and start coding!