Can you explain the essence of the DRY (Don't Repeat Yourself) principle in software development?

The DRY principle — Don't Repeat Yourself — means that the same code or logic should not be duplicated in different parts of the program. This helps to:

• Reduce errors, as changes need to be made in one place.
• Improve code readability and maintainability.
• Simplify testing.

For example, if you need to calculate the sum of array elements in multiple places, it's better to write a function:

function sumArray(arr) {
  return arr.reduce((acc, val) => acc + val, 0);
}

// Usage
const total = sumArray([1, 2, 3, 4]);

Instead of copying the summing code everywhere, we call the function, which makes maintenance easier and improves code structure.