CODEWITHSUNDEEP
javascriptarraysmultidimensional-array
lemontree
lemontree

Reputation: 99

Javascript minesweeper game, can't increment the right cell

I'm writing a simple minesweeper game in Javascript. I have a 2-dimensional array (called "mineInput") to hold the locations of all the mines. And I have a separate array "result" which records the number of mines adjacent to each cell.

I have 2 nested for loops to iterate over each row and each column in "result" and check every sell in 'mineInput". If there is a mine, I increment the mine count with result[i][j]++;. However I noticed weird behavior where the entire column is incremented instead of just one cell.

this:

[ [ 0, 0, 0 ],
  [ 0, 0, 0 ],
  [ 0, 0, 0 ] ]

followed by: result[i][j]++;

becomes:

[ [ 0, 1, 0 ],
  [ 0, 1, 0 ],
  [ 0, 1, 0 ] ]

instead of:

[ [ 0, 0, 0 ],
  [ 0, 1, 0 ],
  [ 0, 0, 0 ] ]

Here is the full code (pls excuse the obscene number of console logs). https://repl.it/BIYH/2

Any idea what's wrong?

Upvotes: 1

Views: 226

Answers (2)

Elian Ebbing
Elian Ebbing

Reputation: 19027

I guess the problem is in the following code:

var result = [];
var newRow = [];
for (var i = 0; i < rowCount; i++) {
  newRow.push(0);
}
for (var i = 0; i < rowCount; i++) {
  result.push(newRow);
}

You add the same array over and over again to the array result. Instead, you want to create a new array for each row:

var result = [];

for (var i = 0; i < rowCount; i++) {
    var newRow = [];
    for (var j = 0; j < rowCount; j++) {
      newRow.push(0);
    }
    result.push(newRow);
}

An array is an object in javascript, and objects are always passed by reference.

Upvotes: 1

David Waters
David Waters

Reputation: 12028

The issue is early in your code where you initialise your arrays

var result = [];
var newRow = [];
for (var i = 0; i < rowCount; i++) {
  newRow.push(0);
}
for (var i = 0; i < rowCount; i++) {
  result.push(newRow);
}

You have created only one newRow array and added it to your result array 3 times. So you could show this like:

newRow == [0,0,0]
result == [newRow, newRow, newRow]

When you increment you add to one cell in the newRow array which gives

newRow == [0,1,0]
result == [newRow, newRow, newRow] therefore
result = [[0,1,0],[0,1,0],[0,1,0]]

you can fix this like this:

var result = [];
for (var i = 0; i < rowCount; i++) {
  // create a new array for each row
  var newRow = [];
  for (var i = 0; i < rowCount; i++) {
    newRow.push(0);
  }

  result.push(newRow);
}

Upvotes: 4

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