== and === in JavaScript

== Operator

The == operator converts the operands to the same type before checking for equality.

The == operator checks for the same value but not the same type of operands.

0 == false                  // true
2 == "2"                    // true
null == undefined           // true

=== Operator

The === operator does not perform any type conversion on the operands before checking for equality.

The === operator checks for both the same value and the same data type of the operands.

0 === false                 // false
2 === '2'                   // false
null === undefined          // false

Using the === operator is considered a best practice in JavaScript.

Questions

1. What will be the output of the following program?

console.log("location" == new String("location"));
console.log("location" === new String("location"));

Answer — true, false

Explanation: In the first console statement, the == operator returns true because it converts both operands to the same type (string) and compares their values, which are equal.

In the second console statement, the === operator returns false because it performs a strict equality comparison, checking not only for the same value but also for the same data type. Since the left-hand operand is a string and the right-hand operand is an object (created using the new String() constructor), they are of different data types, resulting in a false comparison.