Function Style, Method Style

 The main difference between the function style and the use of the `filter()` method lies in the programming paradigm they represent.

1. **Function Style**: The function style represents the procedural programming paradigm. In this style, you write a sequence of commands for the computer to perform. The function `filterArray` that we wrote earlier is an example of this. It uses a `for` loop to iterate over the array and an `if` statement to check each element against the test function. This style gives you more control over the details of how the array is processed.

function filterArray(array, test) {

  let result = [];

  for (let i = 0; i < array.length; i++) {

    if (test(array[i])) {

      result.push(array[i]);

    }

  }

  return result;

}

let isEven = (num) => num % 2 === 0;

let evenNumbers = filterArray(array, isEven);

console.log('Even numbers:', evenNumbers);

2. **Method Style**: The method style represents the functional programming paradigm. In this style, you use built-in array methods like `filter()` to process the array. The `filter()` method abstracts away the details of how the array is processed, allowing you to focus on what you want to do (filter the array) rather than how to do it. This style can lead to more concise and readable code.

let evenNumbers = array.filter(num => num % 2 === 0);

console.log('Even numbers:', evenNumbers);

In general, the method style is considered more "modern" and is often preferred in JavaScript, but both styles have their uses and can be appropriate in different situations.