Why Does Array.fill() Create Shared References in Two-Dimensional Arrays?

Array.fill() Copies References, Not Values

When attempting to initialize a two-dimensional matrix with Array.fill(), you may encounter an issue where the inner arrays share references, causing unexpected results.

To address this problem, you can utilize Array.from():

let m = Array.from({length: 6}, () => Array(12).fill(0));

m[0][0] = 1;
console.log(m[0][0]); // Outputs 1, as expected
console.log(m[1][0]); // Outputs 0, as intended

This approach creates copy-by-value inner arrays, ensuring that modifications to one array do not affect the others. Each inner array is a distinct object, providing the desired independence.

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