Declarative Arrays for Readable Writing

Mastering Declarative Array Methods in JavaScript

JavaScript has undergone significant changes in recent years, with the adoption of ES6 and modern frameworks shifting the focus towards a more declarative approach. In this article, we’ll explore the benefits of using declarative array methods and provide tips on how to use them effectively.

Declarative vs. Imperative Programming

Imperative programming focuses on the commands that the computer should execute, whereas declarative programming focuses on what you want to achieve. While imperative programming can be more performant, declarative programming leads to more readable and maintainable code.

Declarative Array Methods

There are several declarative array methods available in JavaScript, including reduce, map, and filter. These methods allow you to manipulate arrays in a more concise and readable way.

Reduce

The reduce method is one of the most powerful array methods. It works by calling a provided function against each item in the array, accumulating a value that is returned as the final result.

javascript
const numbers = [1, 2, 3, 4, 5];
const sum = numbers.reduce((accumulator, currentValue) => accumulator + currentValue);
console.log(sum); // Output: 15


Map

The map method creates a new array with the results of applying a provided function to each item in the original array.

javascript
const numbers = [1, 2, 3, 4, 5];
const squaredNumbers = numbers.map(number => number * number);
console.log(squaredNumbers); // Output: [1, 4, 9, 16, 25]


Filter

The filter method creates a new array with all items that pass the test implemented by a provided function.

javascript
const numbers = [1, 2, 3, 4, 5];
const evenNumbers = numbers.filter(number => number % 2 === 0);
console.log(evenNumbers); // Output: [2, 4]


Tips for Using Declarative Array Methods

1. Name your callbacks: Give your callback functions descriptive names to make your code more readable.
2. Name your callback arguments: Use descriptive names for your callback arguments to make your code more readable.
3. Choose the right method: Use the most specific method for the job. For example, use map instead of reduce when you need to create a new array.
4. Chain together small functions: Break down complex operations into smaller, more manageable functions that can be chained together.

By following these tips, you can write more readable and maintainable code using declarative array methods.

Real-World Example

Suppose we have an array of objects representing restaurants, and we want to filter out the ones that are not open and do not serve food.

“`javascript
const restaurants = [
{ name: ‘Restaurant 1’, isOpen: true, servesFood: true },
{ name: ‘Restaurant 2’, isOpen: false, servesFood: true },
{ name: ‘Restaurant 3’, isOpen: true, servesFood: false },
];

const openRestaurantsThatServeFood = restaurants
.filter(restaurant => restaurant.isOpen)
.filter(restaurant => restaurant.servesFood)
.map(restaurant => restaurant.name);

console.log(openRestaurantsThatServeFood); // Output: [‘Restaurant 1’]
“`

In this example, we chain together three small functions to achieve the desired result. This makes our code more readable and maintainable.

Conclusion

Declarative array methods are a powerful tool for manipulating arrays in JavaScript. By following the tips outlined in this article, you can write more readable and maintainable code that is easier to understand and modify.