Question
Answer and Explanation
Counting the elements of a 2D array by each row involves iterating through each row of the array and determining the length of that specific row. Here's how you can achieve this in JavaScript, along with explanations:
1. Understanding 2D Arrays:
- A 2D array is an array of arrays. Each inner array can be thought of as a row.
2. Iterating Through Rows:
- Use a for loop (or other iteration methods) to traverse each row (inner array) of the 2D array.
3. Counting Elements in Each Row:
- Within each iteration, use the length property of the current row to get the number of elements in that row.
4. JavaScript Example:
function countElementsByRow(matrix) {
const rowCounts = [];
for (let i = 0; i < matrix.length; i++) {
const rowLength = matrix[i].length;
rowCounts.push(rowLength);
}
return rowCounts;
}
// Example usage:
const myArray = [
[1, 2, 3],
[4, 5],
[6, 7, 8, 9],
[10]
];
const counts = countElementsByRow(myArray);
console.log(counts); // Output: [3, 2, 4, 1]
5. Explanation of the Code:
- The countElementsByRow function takes a 2D array (matrix) as input.
- It initializes an empty array rowCounts to store the counts of elements for each row.
- The for loop iterates through each row of the input array.
- Inside the loop, matrix[i].length obtains the length (number of elements) of the current row.
- This length is then pushed into the rowCounts array.
- Finally, the rowCounts array is returned, holding the count of elements for each row of the 2D array.
This method is straightforward and effective for counting elements in each row of a 2D array. Each element in the resulting array corresponds to the number of elements in the respective row from the original 2D array. Make sure that input array is actually a 2D array.