=== are comparison operators used to compare values. The main differences between these operators are as follows:
1. Type coercion:
== operator performs type coercion, which means it tries to convert the operands to a common type before comparison.
=== operator, also known as the strict equality operator, does not perform type coercion and requires both the value and the type to be the same for equality.
2. Equality comparison:
== operator checks for equality by comparing the values after type coercion.
=== operator checks for equality without performing any type coercion. It compares both the values and types of the operands.
3. Null and undefined:
- In most cases,
undefined are considered equal by the
== operator due to type coercion. For example,
null == undefined returns
=== operator treats
undefined as distinct values, and
null === undefined returns
== operator treats NaN as not equal to anything, including NaN itself. For example,
NaN == NaN returns
=== operator also treats NaN as not equal to anything, including NaN itself. Hence,
NaN === NaN returns
5. Object comparison:
- When comparing objects, both
=== operators check if the operands refer to the same object in memory (i.e., they have the same reference).
- If you compare two different object instances with the same properties and values, the
=== operators will return
false as they refer to different objects.
To summarize, the
== operator performs type coercion and compares the values after conversion, while the
=== operator performs strict equality checks by comparing both the values and types without any type coercion. It's generally recommended to use the
=== operator for equality comparisons in order to avoid unexpected behavior due to type coercion.