How to check if a variable is an array?

Table of Contents

• Introduction
• 1. Using Array.isArray()
  • Example
• 2. Using the instanceof Operator
  • Example
• 3. Using Object.prototype.toString()
  • Example
• Conclusion

Introduction

In JavaScript, arrays are special objects used to store multiple values in a single variable. However, it’s essential to determine whether a given variable is an array before performing array-specific operations. This guide will cover various methods to check if a variable is an array, along with practical examples for each approach.

1. Using Array.isArray()

The most reliable way to check if a variable is an array is by using the built-in Array.isArray() method. This method returns true if the given variable is an array and false otherwise.

Example

2. Using the instanceof Operator

You can also use the instanceof operator to check if a variable is an instance of the Array constructor. This approach works well but may not be reliable in all cases, particularly in situations involving iframes or multiple JavaScript contexts.

Example

3. Using Object.prototype.toString()

Another method to check if a variable is an array is by using the Object.prototype.toString.call() method. This approach can provide a more reliable type check, especially when working across different contexts.

Example

Conclusion

Determining if a variable is an array in JavaScript is crucial for ensuring that your code behaves as expected. The Array.isArray() method is the most straightforward and reliable way to perform this check. While instanceof and Object.prototype.toString() provide alternative methods, they can have their limitations depending on the context. Understanding these methods will enhance your ability to work effectively with arrays in JavaScript.