When to Use Array Square Brackets vs. new Array() for Efficient Array Initialization in JavaScript?

Faster Array Creation: Comparing Array Square Brackets and new Array()

In JavaScript, there are two common ways to create an array: using square brackets ([]) and the new Array keyword. While both methods produce an array, there is a noticeable performance difference between the two. Using square brackets ([]) tends to be faster than new Array.

To understand this difference, let's delve into the underlying compilation process. During lexical analysis, square brackets are always treated as array initialization, and the compiler generates code accordingly. This straightforward token recognition allows for efficient array creation.

On the other hand, using new Array involves additional processing. The compiler must first check the scope chain to identify the Array constructor, which adds overhead. Additionally, the Array constructor is an overloaded function, requiring further checks to determine how to initialize the array based on the arguments provided.

These extra steps in the compilation process account for the slower performance of new Array compared to square brackets ([]). The latter is more direct and requires less overhead, resulting in quicker array creation.

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