What is the difference between == and === for objects?

Table of Contents

• Introduction
• How == and === Operate
  • 1. Loose Equality (==)
  • 2. Strict Equality (===)
• Comparison of == and === for Objects
  • Example 1: Comparing Two Different Object Instances
  • Example 2: Comparing Object with a Primitive Value
  • Example 3: Comparing the Same Object
• Summary of Differences
• Conclusion

Introduction

In JavaScript, the == and === operators are used for comparing values, but they behave differently, especially when it comes to comparing objects. Understanding these differences is crucial for writing reliable and bug-free code. This article will explain how these operators function when comparing objects and provide examples to illustrate their behavior.

How == and === Operate

1. Loose Equality (==)

The loose equality operator == checks for equality between two values, but it allows for type coercion. When comparing objects, if the values being compared are not of the same type, JavaScript attempts to convert one or both of them to a common type before making the comparison.

2. Strict Equality (===)

The strict equality operator === checks for equality without allowing type coercion. It requires that both operands are of the same type and value. When comparing objects, === checks if both operands refer to the exact same object in memory.

Comparison of == and === for Objects

Example 1: Comparing Two Different Object Instances

In this example, even though obj1 and obj2 have the same properties and values, they are two different objects stored in different memory locations. Thus, both == and === return false.

Example 2: Comparing Object with a Primitive Value

Here, the object is being compared to a string representation. Since they are of different types, both comparisons return false.

Example 3: Comparing the Same Object

In this case, both == and === return true because obj and objReference point to the same object in memory.

Summary of Differences

1. Type Coercion:
   • == allows type coercion, which can lead to unexpected results when comparing different types.
   • === does not allow type coercion and checks for strict equality in both type and value.
2. Object Reference:
   • Both == and === compare object references when comparing objects. If two object variables reference the same object, they are considered equal.
3. Best Practices:
   • It is generally recommended to use === for comparisons in JavaScript to avoid potential pitfalls associated with type coercion.

Conclusion

Understanding the differences between the == and === operators in JavaScript is essential for making accurate comparisons, especially with objects. While both operators compare object references, == allows for type coercion, which can lead to unexpected results. To maintain type safety and ensure that your comparisons yield the expected results, it is best to use the strict equality operator === when working with objects and other values in JavaScript.