How Can I Ensure Unique Objects When Using Array.prototype.fill()?

Array.prototype.fill(): Passing Objects as References

The Array.prototype.fill() method is a convenient utility for initializing an array with a specified value. However, when filling an array with objects, the objects are passed as references rather than creating new instances. This behavior raises the question of whether there is a way to ensure that each element of the array is a unique object.

Consider the following example:

var arr = new Array(2).fill({});
console.log(arr[0] === arr[1]); // true

In this example, two objects are created and passed as references to arr[0] and arr[1]. Modifying one element of the array will affect the other, as they are the same object:

arr[0].test = 'string';
console.log(arr[1].test); // 'string'

To create a new object for each element of an array using Array.prototype.fill(), you can follow these steps:

1. Fill the array with any arbitrary value (e.g., undefined) using the fill() method.
2. Use the map() method to create a new array with new instances of the desired object type:

var arr = new Array(2).fill().map(u => ({}));

This approach ensures that each element of the array is a distinct object, isolated from the others:

arr[0].test = 'string';
console.log(arr[1].test); // undefined

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