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Why does pushing to one array affect all the arrays in my two-dimensional array?
I was trying to initialize a simple two dimensional array as follows:
const arrays = Array(3).fill([]);
However, when I tried to push an entry into one of the arrays, it seems like it gets pushed to all of them for some reason:
arrays[0].push('foo');
console.log(arrays); // [ [ 'foo' ], [ 'foo' ], [ 'foo' ] ]
Why is this happening, and what can I do to fix it?
1 answer
The problem is that the fill function is filling the array with references to the same empty array[1], and therefore modifying that array will affect every entry because all of them are actually the same entry.
To get around this, you need to explicitly create a new array for each index, for instance by using a for loop
const arrays = [];
for (let i = 0; i < 3; i++) {
arrays.push([]);
}
arrays[0].push('foo');
console.log(arrays); // [ [ 'foo' ], [], [] ]
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