Difference between equal and strictly equal in javascript

The strict equality operator (===) checks whether its two operands are equal, returning a Boolean result. Unlike the equality operator, the strict equality operator always considers operands of different types to be different.

console.log("hello" === "hello");   // true
console.log("hello" === "hola");    // false

console.log(3 === 3);               // true
console.log(3 === 4);               // false

console.log(true === true);         // true
console.log(true === false);        // false

console.log(null === null);         // true

console.log("3" === 3);           // false

console.log(true === 1);          // false

console.log(null === undefined);  // false

const object1 = {
  name: "hello"
}

const object2 = {
  name: "hello"
}

console.log(object1 === object2);  // false
console.log(object1 === object1);  // true

Specifications

Browser compatibility

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What is = in JavaScript?

Equal to (=) is an assignment operator, which sets the variable on the left of the = to the value of the expression that is on its right. This operator assigns lvalue to rvalue.

For example, Writing a=10 is fine. If we write 10=10, ‘a’ = 10 or ‘a’ = ‘a’, it will result in a reference error.

In this tutorial, you will learn:

• What is = in JavaScript?
• What is == in JavaScript?
• What is === in JavaScript?
• Why use = in JavaScript?
• Why use == in JavaScript?
• How === Works Exactly?
• Example of =
• Example of ==
• Example of ===
• = Vs == VS === in JavaScript

What is == in JavaScript?

Double equals (==) is a comparison operator, which transforms the operands having the same type before comparison.

So, when you compare string with a number, JavaScript converts any string to a number. An empty string is always converts to zero. A string with no numeric value is converts to NaN (Not a Number), which returns false.

What is === in JavaScript?

=== (Triple equals) is a strict equality comparison operator in JavaScript, which returns false for the values which are not of a similar type. This operator performs type casting for equality. If we compare 2 with “2” using ===, then it will return a false value.

Why use = in JavaScript?

Here are the important uses of = in JavaScript:

= JavaScript operator assigns a value to the left operand depends on the value of operand available on the right side. The first operand should be a variable.

The basic assignment operator is =, that assigns the value of one operand to another. That is, a = b assigns the value of b to a.

Why use == in JavaScript?

Here are the important uses of == in JavaScript:

The == operator is an equality operator. It checks whether its two operands are the same or not by changing expression from one data type to others. You can use == operator in order to compare the identity of two operands even though, they are not of a similar type.

How === Works Exactly?

• Strict equality === checks that two values are the same or not.
• Value are not implicitly converted to some other value before comparison.
• If the variable values are of different types, then the values are considered as unequal.
• If the variable are of the same type, are not numeric, and have the same value, they are considered as equal.
• Lastly, If both variable values are numbers, they are considered equal if both are not NaN (Not a Number) and are the same value.

Example of =

In the below program, there are two variables “a” and “b”. We are adding and printing their values using a third variable, “c”. The sum of the value of variable “a” and “b” is 7. Therefore, the output is 7.

JavaScript Operators

 
a = 2, b = 5, calculate c = a + b, and display c:
 

Output:

a = 2, b = 5, calculate c = a + b, and display c:

7

Example of ==

In the below program, we have declared one variable “a” having value 10. Lastly, the statement a == 20 returns false as the value of a is 10.

Output:

false

Example of ===

In the below program, the value of variable x is 10. It is compared to 10 written in double-quotes, which is considered as a string, and therefore, the values are not strictly the same. The output of the program is false.

Output:

false

= Vs == VS === in JavaScript

Here are the important differences between =, ==, and ===

KEY DIFFERENCES:

• = is used for assigning values to a variable, == is used for comparing two variables, but it ignores the datatype of variable whereas === is used for comparing two variables, but this operator also checks datatype and compares two values.
• = is called as assignment operator, == is called as comparison operator whereas It is also called as comparison operator.
• = does not return true or false, == Return true only if the two operands are equal while === returns true only if both values and data types are the same for the two variables.