How Can I Best Determine if a JavaScript Variable is an Array?

Checking if a Variable is an Array in JavaScript

Determining whether a variable is an array in JavaScript is crucial for various programming scenarios. To achieve this, several methods exist.

Recommended Method:

The optimal approach, as you have mentioned, is to check the constructor property:

variable.constructor === Array

This method is the fastest and most accurate since all arrays are objects, and JavaScript engines efficiently evaluate the constructor property.

Other Methods:

• Array.isArray(variable): This method is explicit and specifically designed for arrays. It returns a boolean indicating if the variable is an array.
• variable instanceof Array: This method checks if the variable is an instance of the Array class. While it's slower than checking the constructor, it's still relatively efficient.
• Object.prototype.toString.call(variable) === '[object Array]': This method checks the object's toString() method, which returns a string describing the object's type. For arrays, it returns "[object Array]". However, it's the slowest of the suggested methods.

Important Note:

If you encounter null or undefined values, you may need to perform additional checks to ensure that a property exists before attempting to verify if it's an array.

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