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Table of Contents
What is Type Coercion?
Why Use === Instead of ==?
When Might You Use ==?
Home Web Front-end JS Tutorial What is the difference between == and === in JavaScript?

What is the difference between == and === in JavaScript?

Jul 09, 2025 am 02:41 AM
comparison operator

The main difference between == and === in JavaScript is type coercion handling. 1. == performs type coercion, converting data types to match before comparison, which can lead to unexpected results like "5" == 5 returning true or [] == ![] returning true. 2. === compares both value and type strictly without conversion, making it more predictable, so "5" === 5 returns false. 3. Use === for safer comparisons avoiding surprises, especially with objects where === checks reference identity. 4. == might be used intentionally only in specific cases like checking null or undefined together. Most style guides recommend always using === for clarity and reliability.

What is the difference between == and === in JavaScript?

In JavaScript, the main difference between == and === lies in how they compare values. The == operator checks for equality after performing type coercion if needed, while === checks for both value and type equality without any type conversion.

What is the difference between == and === in JavaScript?

What is Type Coercion?

Type coercion happens when JavaScript automatically converts one data type to another to make a comparison work. This is where == comes into play. For example:

  • 5 == "5" returns true because JavaScript converts the string "5" to the number 5 before comparing.
  • 0 == false also returns true because both are considered falsy values and are coerced into similar types during comparison.

This behavior can be confusing, especially when you're not expecting it. It's easy to end up with unexpected results if you're not careful.

What is the difference between == and === in JavaScript?

Some common examples of surprising behavior with ==:

  • "" == 0true
  • null == undefinedtrue
  • [] == ![]true

These might seem illogical at first glance, but they happen due to internal rules JavaScript uses during type coercion.

What is the difference between == and === in JavaScript?

Why Use === Instead of ==?

Using === avoids surprises from type coercion. If the types of the two operands are different, === immediately returns false. So:

  • 5 === "5"false (number vs string)
  • 0 === falsefalse (number vs boolean)

This makes your code more predictable and easier to debug. In general, unless you have a specific reason to allow type coercion, it’s safer to use ===.

Also, when comparing objects or arrays, even if they look identical, === will only return true if both variables reference the exact same object in memory.

Examples:

  • { a: 1 } === { a: 1 }false (two separate objects)
  • let a = []; a === atrue

When Might You Use ==?

There are a few rare cases where using == might be intentional:

  • When you want to check whether a value is either null or undefined in one go:
    value == null will return true if value is null or undefined.

  • Simplifying comparisons where you know types may vary slightly but mean the same thing logically (e.g., numeric strings).

Even so, these cases are exceptions rather than the rule. Most modern JavaScript style guides recommend avoiding == altogether to prevent subtle bugs.


So, basically, always prefer === unless you fully understand the implications of type coercion. It keeps your logic clean and avoids confusion down the line.

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