What is the difference between == and === in JavaScript
Jul 13, 2025 am 02:19 AMIn JavaScript, the main difference between == and === is type coercion. 1. == compares values after converting types if necessary, which can lead to unexpected results. 2. === compares both value and type without conversion, making it more predictable. For example, 5 == '5' is true but 5 === '5' is false. Use === for clarity and safety, and == only when intentional type coercion is needed.
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.
Type Coercion with ==
The ==
operator tries to make the operands the same type before comparing them. This means that if the types are different, JavaScript will attempt to convert one or both of the operands into a common type.
- For example:
-
5 == '5'
returnstrue
, because JavaScript converts the string'5'
into a number before comparing. -
0 == false
also returnstrue
, since both are considered falsy values and are coerced into each other's type.
-
This behavior can sometimes lead to confusing or unexpected results, especially when dealing with different data types like strings, numbers, booleans, or null
and undefined
.
Strict Comparison with ===
The ===
operator, on the other hand, does not perform type coercion. It compares both the value and the type of the operands directly.
- Using the earlier examples:
-
5 === '5'
returnsfalse
, because although the values look the same, their types (number vs string) are different. -
0 === false
also returnsfalse
for the same reason—different types.
-
This makes ===
more predictable and safer to use in most cases, especially when you want to ensure that both the value and its type match exactly.
When to Use Which
If you're writing code where type matters—and it usually does—you should go with ===
. It avoids surprises from automatic type conversion and makes your logic clearer.
However, there are rare situations where you might intentionally want coercion, such as when you expect mixed types but still want to treat them as equal (e.g., checking if a value is either 0
or the boolean false
). In those cases, ==
might be appropriate—but use it carefully.
Basically, stick with ===
unless you have a specific reason to use ==
.
The above is the detailed content of What is the difference between == and === in JavaScript. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

In PHP, the "==" symbol is a comparison operator that can compare whether two operands are equal. The syntax is "operand 1 == operand 2". The "==" operator compares and tests whether the variable on the left (expression or constant) has the same value as the variable on the right (expression or constant); it only compares the values ??of the variables, not the data types. If the two values ??are the same, it returns a true value; if the two values ??are not the same, it returns a false value.

Introduction to python operators Operators are special symbols or keywords used to perform operations between two or more operands. Python provides a variety of operators covering a wide range of uses, from basic mathematical operations to complex data manipulation. Mathematical operators Mathematical operators are used to perform common mathematical operations. They include: operator operation examples + addition a + b - subtraction a-b * multiplication a * b / division a / b % modulo operation (take the remainder) a % b ** power operation a ** b // integer division (discard the remainder) a//b Logical Operators Logical operators are used to concatenate Boolean values ??and evaluate conditions. They include: operator operations examples and logical and aandbor logical or aorbnot logical not nota comparison operations

The Secret Garden of Operators Python operators are symbols or keywords used to perform various operations. They enable developers to express complex logic concisely and clearly and improve code efficiency. Python provides a wide range of operator types, each with its specific purpose and usage. Logical Operators Logical operators are used to combine Boolean values ??and perform logical operations. The main ones are: and: Returns the Boolean value True, if all operands are True, otherwise it returns False. or: Returns a Boolean value True if any operand is True, otherwise returns False. not: Negate the Boolean value, change True to False, and change False to True. Demo code: x=Truey

Python operators are a key component of the programming language, enabling developers to perform a wide range of operations, from simple arithmetic to complex bit manipulation. Mastering the syntax, semantics, and functionality of operators is essential to using Python effectively. Arithmetic Operators Arithmetic operators are used to perform basic arithmetic operations. They include addition (+), subtraction (-), multiplication (*), division (/), modulo (%), exponentiation (**), and floor division (//). The following example demonstrates the use of arithmetic operators: >>a=10>>b=5#Addition c=a+bprint(c)#Output: 15#Subtraction c=a-bprint(c)#Output: 5#Multiplication c=a*bprint(c)#output

Equality comparison in PHP involves the == operator. It has two types: strict comparison (===) and non-strict comparison (==). The latter can produce unexpected results because variables of different types can be converted to the same type and then compared. To ensure that values ??are equal and of the same type, use strict comparison.

In PHP, the main difference between == and == is the strictness of type checking. ==Type conversion will be performed before comparison, for example, 5=="5" returns true, and ===Request that the value and type are the same before true will be returned, for example, 5==="5" returns false. In usage scenarios, === is more secure and should be used first, and == is only used when type conversion is required.

In PHP, the three equal signs "===" are congruent comparison operators, used to compare whether the values ??of two operands are equal; this operator performs a strict comparison between given variables or values ??and will compare and see if two variables (expressions or constants) are equal in value and have the same data type, i.e. both are strings or both are integers and so on. This operator returns true if two variables (expressions or constants) contain the same value and the same data type, otherwise it returns false.

Python operators are special symbols or words used to perform specific operations on values ??or to combine values. They are the fundamental building blocks of programming languages ??and are key to understanding and writing efficient code. Arithmetic Operators Arithmetic operators are used to perform basic mathematical operations such as addition, subtraction, multiplication, division, and remainder. The following are the most commonly used arithmetic operators: +Addition-Subtraction*Multiplication/Division%Remainder Example: x=10y=5print(x+y)#Output: 15print(x-y)#Output: 5print(x*y)#Output :50print(x/y)#Output: 2.0print(x%y)#Output: 0 Comparison Operator The comparison operator is used to compare two values ??and return a Boolean value (True
