problem with assigning value to a 2d array javascript (node.js)

Question

the problem I have is when I associate value in the 2d array on a certain row and column, that value will be stored on several rows on the same column

var Matrix = Array(3).fill(Array(3).fill(0));
console.log(Matrix);
Matrix[1][2]=1;
console.log(Matrix);

and the output is : 

/// the 2d array 
[ [ 0, 0, 0 ], [ 0, 0, 0 ], [ 0, 0, 0 ] ]
/// after 'Matrix[1][2]=1'
[ [ 0, 0, 1 ], [ 0, 0, 1 ], [ 0, 0, 1 ] ]

You're assigning a reference to the same "inner" array to all the positions in the outer one. — Andreas is moving to Codidact, Jul 12 '20 at 00:02
`const matrix = Array.from(Array(3), () => Array(3).fill(0));` — Patrick Roberts, Jul 12 '20 at 00:14
@Andreas so what are you saying is that : all those arrays are just like mirrors , they are the same thing , right ? if is that then thanks . — picantultunic, Jul 12 '20 at 00:57

score 1 · Answer 1 · answered Jul 12 '20 at 00:14

1

The tree sub-arrays you are declared in the first line, are refered to the same array, like a pointer.

try something like this:

var Matrix = []
Matrix.push(Array(3).fill(0))
Matrix.push(Array(3).fill(0))
Matrix.push(Array(3).fill(0))
console.log(Matrix);
Matrix[1][2]=1;
console.log(Matrix);

Output

/// the 2d array 
[ [ 0, 0, 0 ], [ 0, 0, 0 ], [ 0, 0, 0 ] ]
/// after 'Matrix[1][2]=1'
[ [ 0, 0, 0 ], [ 0, 0, 1 ], [ 0, 0, 0 ] ]

answered Jul 12 '20 at 00:14

Nicolas Acosta

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5
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it's working , thanks . – picantultunic Jul 12 '20 at 01:01

problem with assigning value to a 2d array javascript (node.js)

1 Answers1