JavaScript’s Array.prototype.includes()
method is a powerful yet often overlooked tool for efficiently searching arrays. This article delves into its functionality, practical applications, and crucial considerations, demonstrating how it can significantly enhance game development logic through a real-world example from a Pac-Man project.
Understanding `Array.prototype.includes()`
At its core, Array.prototype.includes()
is a built-in JavaScript method designed to determine whether an array contains a specified element. It provides a simple true
or false
response, indicating the presence or absence of the value in question.
Syntax:
array.includes(element, fromIndex)
- `element`: The value that the method searches for within the array.
- `fromIndex` (optional): An integer representing the position in the array at which to begin the search. If omitted, the search starts from index 0.
Practical Applications and Simple Checks
The .includes()
method excels at straightforward value verification. For instance, in a game, you might want to check if a player has collected a specific item. Consider this example from a Pac-Man game where it’s used to identify bonus fruits:
const fruitBonus = ['🍒', '🍓', '🍊', '🍊', '🍎', '🍎', '🍈', '🍈', '🚀', '🔔', '🔑'];
console.log(fruitBonus.includes('🍎')); // true (Apple is present)
console.log(fruitBonus.includes('🍉')); // false (Watermelon is not in the array)
As illustrated, .includes()
effectively handles various primitive types, including strings, numbers, and even emojis, providing immediate feedback on an element’s presence.
Important Considerations and Limitations
While incredibly useful, it’s vital to understand the limitations of .includes()
. This method performs a strict equality comparison (similar to ===
). Consequently, it works flawlessly for primitive values (numbers, strings, booleans, symbols, undefined
, null
).
However, .includes()
does not perform deep checks for nested arrays or objects. When searching for an object or array, it will only return true
if the exact same reference to that object or array exists in the array being searched. If you need to compare the contents of objects or arrays, you’ll need a different approach, such as using Array.prototype.some()
combined with a custom comparison function.
Enhancing Game Logic with `.includes()`: A Pac-Man Example
One compelling application of .includes()
is in refining game AI, as demonstrated in a JavaScript Pac-Man project to control ghost movement. By identifying key “intersection” points on the game board, ghosts can be programmed to intelligently change direction, mimicking the behavior of the original arcade game.
An intersectionIndices
array is defined, containing the specific indices on the game grid that represent these crucial intersections:
export const intersectionIndices = [
34, 49, 141, 146, 149, 152, 155, 158, 161, 166,
230, 245, 320, 323, 377, 378, 398, 401, 410, 413,
485, 494, 566, 569, 578, 581, 650, 653, 656, 659,
662, 665, 731, 752, 824, 827
];
During the game board’s construction, each square’s index is checked against this array. If an index is found within intersectionIndices
using .includes()
, that square is dynamically assigned an 'intersection'
CSS class, both visually and logically marking it as a critical point for game mechanics:
export function buildTheBoard() {
for(let i = 0; i < 868; i++) {
let div = document.createElement("div");
gameGrid.appendChild(div);
squares.push(div);
squares[i].classList.add('game-board-square');
if (intersectionIndices.includes(i)) { // Here's .includes() in action!
squares[i].classList.add('intersection');
}
}
}
To streamline game logic, a helper function, isIntersection()
, leverages .includes()
to quickly determine if any given index
corresponds to an intersection:
// Helper function to check if a given index is an intersection
function isIntersection(index) {
return intersectionIndices.includes(index);
}
This isIntersection()
function is then integrated into the ghost movement logic. When a ghost's currentIndex
is an intersection, the game can trigger a sophisticated direction-changing mechanism, preventing ghosts from making U-turns unless necessary and choosing valid paths that aren't blocked by walls or other game elements. This intelligent use of .includes()
makes the ghost AI more dynamic and the gameplay more aligned with the classic Pac-Man experience.
// Excerpt from ghost movement logic
export function moveGhost(ghost) {
const directions = [-1, 1, 28, -28];
let direction = ghost.direction || directions[Math.floor(Math.random() * directions.length)];
ghost.timerId = setInterval(function() {
// ...existing movement logic...
// At intersections, choose a new direction
if (isIntersection(ghost.currentIndex)) { // Using the helper function
const reverseDir = ghost.previousIndex - ghost.currentIndex;
let validDirections = directions.filter(dir => {
if (dir === reverseDir) return false;
const nextIndex = ghost.currentIndex + dir;
return (
!squares[nextIndex].classList.contains('ghost') &&
!squares[nextIndex].classList.contains('lairText') &&
!squares[nextIndex].classList.contains('wall') &&
!(dir === 28 && squares[nextIndex].classList.contains('lairWall')) &&
(nextIndex !== 375) &&
(nextIndex !== 380)
);
});
if (validDirections.length === 0) {
validDirections = [reverseDir];
}
if (validDirections.length > 0) {
direction = validDirections[Math.floor(Math.random() * validDirections.length)];
ghost.direction = direction;
}
}
// ...rest of movement logic...
}, ghost.speed);
}
By intelligently applying .includes()
to detect intersections, the ghost AI gains a crucial layer of sophistication, moving closer to the authentic and challenging gameplay of the original arcade classic.
Conclusion
The JavaScript Array.prototype.includes()
method is a remarkably straightforward yet effective tool for checking the presence of a primitive value within an array. Its simplicity makes it ideal for quick verifications, and when combined with thoughtful game design, it can lead to significantly improved gameplay mechanics, such as the intelligent ghost movements in our Pac-Man example. Understanding its capabilities and limitations is key to leveraging its full potential in your projects. We encourage you to experiment with .includes()
to simplify your array checks and discover how it can enhance the features and logic in your own development endeavors.