Does `Array.prototype.fill()` Create New Object Instances, or Share References?

Array.prototype.fill() with Objects: Reference Sharing, Not Instance Creation

When using Array.prototype.fill() with an object, it's important to note that it passes a reference to the same object instance instead of creating new instances for each element. This behavior is demonstrated by the following code:

var arr = new Array(2).fill({});
arr[0] === arr[1]; // true (they point to the same object)
arr[0].test = 'string';
arr[1].test === 'string'; // true (changes made to one object are reflected in the other)

To avoid this reference sharing and ensure that each element holds a unique object instance, the map() function can be used:

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

In these cases, map() creates new objects for each element, eliminating the reference sharing issue.

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