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Screening 01 #1

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123 changes: 104 additions & 19 deletions pages/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,7 @@ const Cell = ({ x, y, type }) => {
const getRandomCell = () => ({
x: Math.floor(Math.random() * Config.width),
y: Math.floor(Math.random() * Config.width),
createdAt: Date.now()
});

const Snake = () => {
Expand All @@ -73,18 +74,31 @@ const Snake = () => {

// snake[0] is head and snake[snake.length - 1] is tail
const [snake, setSnake] = useState(getDefaultSnake());
const [direction, setDirection] = useState(Direction.Right);

const [food, setFood] = useState({ x: 4, y: 10 });
const [direction, setDirection] = useState(() => Direction.Right);
//const time = new Date();
const foodArray = [{ x: 4, y: 10, createdAt: Date.now() }];
const [food, setFood] = useState(foodArray);
const [score, setScore] = useState(0);

// move the snake
useEffect(() => {
const runSingleStep = () => {
setSnake((snake) => {
const head = snake[0];
const newHead = { x: head.x + direction.x, y: head.y + direction.y };

if (newHead.y < 0)
newHead.y = 24;
else if (newHead.y > 24)
newHead.y = 0;
else if (newHead.x < 0)
newHead.x = 24;
else if (newHead.x > 24)
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this checking works but a better approach would have been using mod operation on the newHeads coordinates so they always lie between 0 - 24
like this x = (head.x + direction.x) % Config.width
but this calculation can produce a bug, can you find out ?

newHead.x = 0;
if (isSnake(newHead)) {
setSnake(() => getDefaultSnake());
setDirection(() => Direction.Right);
setFood([{ x: 4, y: 10, createdAt: Date.now() }]);
setScore(() => 0);
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when using a setState, if you need the previous value of the state, you can use a function like this
setState((previousValue) => returnCalculatedNewValue)
but if the new value is independant of the previous one, you can simply set it
setState(independantNewValue)

}
// make a new snake by extending head
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax
const newSnake = [newHead, ...snake];
Expand All @@ -101,41 +115,111 @@ const Snake = () => {

return () => clearInterval(timer);
}, [direction, food]);
//update food
useEffect(() => {
const updateFood = () => {
setFood((food) => {
const foodCell = getRandomCell();
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a random cell can be a food or a snake cell already, we should check if it is not and only allow a cell that isn't already a snake/food.
condition should look like this: isFood(foodCell) || isSnake(foodCell)

const newFood = [...food, foodCell];
return newFood;
});
};
const timer = setInterval(updateFood, 3000);
return () => clearInterval(timer);
}, [])
useEffect(() => {
const updateFood = () => {
setFood((food) => {
const newFood = food.filter(f => Math.floor((Date.now() - f.createdAt) / 1000) < 10.00)
return newFood;
});
};
updateFood();
const timer = setInterval(updateFood, 500);
return () => clearInterval(timer);
}, [])

// update score whenever head touches a food
useEffect(() => {
const head = snake[0];
if (isFood(head)) {
const prevFood = food.filter(f => f.x != head.x && f.y != head.y)
setScore((score) => {
return score + 1;
});
setSnake((snake) => {
const newHead = { x: head.x + direction.x, y: head.y + direction.y };
if (newHead.y < 0)
newHead.y = 24;
else if (newHead.y > 24)
newHead.y = 0;
else if (newHead.x < 0)
newHead.x = 24;
else if (newHead.x > 24)
newHead.x = 0;
if (isSnake(newHead)) {
setSnake(() => getDefaultSnake());
setDirection(() => Direction.Right);
setFood([{ x: 4, y: 10, createdAt: Date.now() }]);
setScore(() => 0);
}
else {
let newFood = getRandomCell();
while (isSnake(newFood)) {
newFood = getRandomCell();
}
setFood([...prevFood, newFood]);
}
const newSnake = [newHead, ...snake];
return newSnake;
});

let newFood = getRandomCell();
while (isSnake(newFood)) {
newFood = getRandomCell();
}

setFood(newFood);
}


}, [snake]);

useEffect(() => {
const handleNavigation = (event) => {

switch (event.key) {
case "ArrowUp":
setDirection(Direction.Top);
case "ArrowRight":
setDirection((prevDirection) => {
if (prevDirection.x == -1 && prevDirection.y == 0)
return Direction.Left;
else
return Direction.Right;
});
break;

case "ArrowDown":
setDirection(Direction.Bottom);
case "ArrowLeft":
setDirection((prevDirection) => {
if (prevDirection.x == 1 && prevDirection.y == 0)
return Direction.Right;
else
return Direction.Left;
});
break;

case "ArrowLeft":
setDirection(Direction.Left);

case "ArrowUp":
setDirection((prevDirection) => {
if (prevDirection.x == 0 && prevDirection.y == 1)
return Direction.Bottom;
else
return Direction.Top;
});
break;

case "ArrowRight":
setDirection(Direction.Right);
case "ArrowDown":

setDirection((prevDirection) => {
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by creating a helper function that takes in the directions and calculates the next direction, you can remove the redundancy

if (prevDirection.x == 0 && prevDirection.y == -1)
return Direction.Top;
else
return Direction.Bottom;
});
break;
}
};
Expand All @@ -146,7 +230,8 @@ const Snake = () => {

// ?. is called optional chaining
// see: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining
const isFood = ({ x, y }) => food?.x === x && food?.y === y;
const isFood = ({ x, y }) =>
food.find((position) => position.x === x && position.y === y);

const isSnake = ({ x, y }) =>
snake.find((position) => position.x === x && position.y === y);
Expand Down