Learn Intermediate OOP by Building a Platformer Game - Step 59

JavaScript
1

Tell us what’s happening:I don’t understand what we ask me.

const canvas = document.getElementById("canvas");
const startScreen = document.querySelector(".start-screen");
const checkpointScreen = document.querySelector(".checkpoint-screen");
const checkpointMessage = document.querySelector(".checkpoint-screen > p");
const ctx = canvas.getContext("2d");
canvas.width = innerWidth;
canvas.height = innerHeight;
const gravity = 0.5;
let isCheckpointCollisionDetectionActive = true;

const proportionalSize = (size) => {
  return innerHeight < 500 ? Math.ceil((size / 500) * innerHeight) : size;
}

class Player {
  constructor() {
    this.position = {
      x: proportionalSize(10),
      y: proportionalSize(400),
    };
    this.velocity = {
      x: 0,
      y: 0,
    };
    this.width = proportionalSize(40);
    this.height = proportionalSize(40);
  }
  draw() {
    ctx.fillStyle = "#99c9ff";
    ctx.fillRect(this.position.x, this.position.y, this.width, this.height);
  }
  
  update() {
    this.draw();
    this.position.x += this.velocity.x;
    this.position.y += this.velocity.y;

    if (this.position.y + this.height + this.velocity.y <= canvas.height) {
      if (this.position.y < 0) {
        this.position.y = 0;
        this.velocity.y = gravity;
      }
      this.velocity.y += gravity;
    } else {
      this.velocity.y = 0;
    }

    if (this.position.x < this.width) {
      this.position.x = this.width;
    }

    if (this.position.x >= canvas.width - 2 * this.width) {
      this.position.x = canvas.width - 2 * this.width;
    }
  }
}

const player = new Player();


const animate = () => {
  requestAnimationFrame(animate);
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  player.update();

  if (keys.rightKey.pressed && player.position.x < proportionalSize(400)) {
    player.velocity.x = 5;
  } else if (keys.leftKey.pressed && player.position.x > proportionalSize(100)) {
    player.velocity.x = -5;
  } else {
    player.velocity.x = 0;
  }
}


const keys = {
  rightKey: {
    pressed: false
  },
  leftKey: {
    pressed: false
  }
};

const movePlayer = (key, xVelocity, isPressed) => {
  if (!isCheckpointCollisionDetectionActive) {
    player.velocity.x = 0;
    player.velocity.y = 0;
    return;
  }

  switch (key) {
    case "ArrowLeft":
      keys.leftKey.pressed = isPressed;
      if (xVelocity === 0) {
        player.velocity.x = xVelocity;
      }
      player.velocity.x -= xVelocity;
      break;
    case "ArrowUp":
    case " ":
    case "Spacebar":
      player.velocity.y -= 8;
      break;
    case "ArrowRight":
      keys.rightKey.pressed = isPressed;
      if (xVelocity === 0) {
        player.velocity.x = xVelocity;
      }
      player.velocity.x += xVelocity;
  }
}


const startGame = () => {
  canvas.style.display = "block";
  startScreen.style.display = "none";
  player.draw();
}

startBtn.addEventListener("click", startGame);

window.addEventListener("keydown",(event)=>{movePlayer(key, xVelocity, isPressed)});

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Challenge Information:

Learn Intermediate OOP by Building a Platformer Game - Step 59

2

The challenge asks you not to use the event parameter but destruct from it the key property, and the challenge didn’t ask about any code in that function yet so you need to remove what is inside your function

movePlayer(key, xVelocity, isPressed)

and leave it empty for that step.

1 Like
3

Just to expand a little.

The event object has a bunch of properties on it. If you only need one specific property and not the event object you can use object destructuring with the function parameter.

For example, the click target. If we change the startGame function you can see how that might work.

const startGame = ({ target }) => {
  target.innerText = 'Started';
}

startBtn.addEventListener("click", startGame);
1 Like
4

thank you I solved this issue thank to your indications

5

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