Input Direction confusion in snake game javascript

[shivajikobardan]

TL;DR Summary

javascript snake game

Here's the full code:



This is the code that I'm interested in:

window.addEventListener("keydown", e => {
  inputDir = { x: 0, y: 1 };
  moveSound.play();
  switch (e.key) {
    case "ArrowUp":
      inputDir.x = 0;
      inputDir.y = -1;
      break;

    case "ArrowDown":
      inputDir.x = 0;
      inputDir.y = 1;
      break;

    case "ArrowLeft":
      inputDir.x = -1;
      inputDir.y = 0;
      break;

    case "ArrowRight":
      inputDir.x = 1;
      inputDir.y = 0;
      break;
  }

})

What is inputDir variable? (I didn't write this code, I'm learning it from a tutorial, you know tutorials don't cover stuffs well).
What I'm not understanding is why are we setting inputDir at 0th row, 1st column? What does that mean? Can you provide some explanations with figures(if possible) about this issue?

 

[pbuk]

What is inputDir variable?

What do you think it could be: inputDirectory? inputDirection?

What I'm not understanding is why are we setting inputDir at 0th row, 1st column?

You need to make a better guess if you think that inputDir represents row and column coordinates (rather than a vector). Anyway the code is terrible - among other things it makes no sense to set inputDir before you have worked out what key is pressed.

 

[willem2]

You need to make a better guess if you think that inputDir represents row and column coordinates (rather than a vector). Anyway the code is terrible - among other things it makes no sense to set inputDir before you have worked out what key is pressed.

You might want to have a default value for inputdir, if a non-arrowkey is pressed. x=0, y=0 (for no movement) would probably make more sense.

 

[shivajikobardan]

You need to make a better guess if you think that inputDir represents row and column coordinates (rather than a vector). Anyway the code is terrible - among other things it makes no sense to set inputDir before you have worked out what key is pressed.

But,

let snakeArr = [
  {
    x: 13,
    y: 15
  }
]

here, x and y represented the location of grid. So, should not here x,y mean the same? I am not getting it.

 

[pbuk]

I am not getting it.

Really? Do you understand the difference between saying an item is at (5, 6) (coordinates) and an item moves by (0, -1) (a vector)?

 

[shivajikobardan]

Really? Do you understand the difference between saying an item is at (5, 6) (coordinates) and an item moves by (0, -1) (a vector)?

but why are we using same variable names for 2 different things? is the question.

 

[pbuk]

but why are we using same variable names for 2 different things? is the question.

I don't understand what you mean: what name are you referring to?

 

[shivajikobardan]

But,

let snakeArr = [
  {
    x: 13,
    y: 15
  }
]

here, x and y represented the location of grid. So, should not here x,y mean the same? I am not getting it.

this x,y and x,y of inputDir.

 

[shivajikobardan]

Really? Do you understand the difference between saying an item is at (5, 6) (coordinates) and an item moves by (0, -1) (a vector)?

exactly that difference is what I'm talking about. Why are we able to use same variable name for 2 different things, one is (5,6) location, another is movement by (0,-1)..

 

[pbuk]

x and y are not variable names, they are object keys (aka property names). It would help if you used better labels and then it would be clear that

directionVector.x; // is the x-component of the direction vector; and
snakeCoordinates[0].x // is the x-coordinate of the head of the snake.

 

[shivajikobardan]

x and y are not variable names, they are object keys (aka property names). It would help if you used better labels and then it would be clear that

directionVector.x; // is the x-component of the direction vector; and
snakeCoordinates[0].x // is the x-coordinate of the head of the snake.

yeaah I now kinda get it.

 

[shivajikobardan]

x and y are not variable names, they are object keys (aka property names). It would help if you used better labels and then it would be clear that

directionVector.x; // is the x-component of the direction vector; and
snakeCoordinates[0].x // is the x-coordinate of the head of the snake.

thanks for the info.