Mathematical expression for Loopback 3 between query on MongoDB

Question

I'm using loopback 3 and MongoDB.

Loopback 3 has between operator and I use it as follows.

whereQuery.progress = { between: [25, 50] };

Which is the correct mathematical expression for above and why?

1. 25 < progress < 50
2. 25 ≤ progress < 50
3. 25 ≤ progress ≤ 50
4. 25 ≤ progress ≤ 50

Answer 1

It is 25 ≤ progress ≤ 50.

Quoting from the linked docs:

True if the value is between the two specified values: greater than or equal to first value and less than or equal to second value.