What's the difference between a == null and a === null? [duplicate]

Question

Can someone help me by explaining the difference. From what I understand the === does an exact match but what does this mean when comparing with null ?

Answer 1

What does this mean when comparing with null?

It means exactly what you already said: It checks whether the value is exactly null.

---

a === null is true if the value of a is null.

See The Strict Equality Comparison Algorithm in the specification:

1. If Type(x) is different from Type(y), return false.
2. If Type(x) is Undefined, return true.
3. If Type(x) is Null, return true.

So, only if Type(a) is Null, the comparison returns true.

Important: Don't confuse the internal Type function with the typeof operator. typeof null would actually return the string "object", which is more confusing than helping.

---

a == null is true if the value of a is null or undefined.

See The Abstract Equality Comparison Algorithm in the specification:

2. If x is null and y is undefined, return true.
3. If x is undefined and y is null, return true.