yea 1/x is not strictly defined for x=0, but you can extend it in ℜ ∪ {+∞,-∞}, I don't know your math background, but 1/-0 could make you think of limits: 1/0

yea 1/x is not strictly defined for x=0, but you can extend it in ℜ ∪ {+∞,-∞}, I don't know your math background, but 1/-0 could make you think of limits: 1/0 is like 1/0⁺ (limit of 1/x in ]0,+∞[ when x->0) == Infinity. 1/-0 is like 1/0⁻ (limit of 1/x in ]-∞,0[ when x->0) == -Infinity. 1/Infinity is 0 .... 0/0 is however an indefinite form, so it's NaN so the behavior of JS makes sense And even if 1/0 and 1/-0 returned NaN, they wouldn't be equal to each other too