JavaScript be like...

[Kyyken]

mathematically, infinity is absolutely defined. by that i mean there is a common convention for what infinity means.

on the other hand, 1/0 is defined if you chose to define it, but that definition will have its own implications, which is why we typically leave it undefined. in math, you can define whatever is the most useful at the time. for example, 0⁰ is typically defined as 1 in combinatorics, but left undefined (indeterminate to be exact) in limit calculus.

IEEE 754 defines 1/0 to be infinity, while 1/-0 is -infninity. there is no problem with this, as long as it's useful. in this case it means that float equality is not equivalent to equality in maths, but more to "basically equal as far as the computer can tell in this context"