var a = 9/0;
a;
Infinity
typeof a;
"number"
typeof 9/0;
NaN
typeof NaN
"number"
var a = 9/0;
a;
Infinity
typeof a;
"number"
typeof 9/0;
NaN
typeof NaN
"number"priority ratio of
typeof
typeof (9pm 0) is' number'
Infinity is infinity, is a number
similar
var a = 1;
typeof a*1
NaNvar a = 1;
typeof (a*1)
NUmber the reason is that the parameters after typeof do not participate in the calculation, so typeof 9 Infinity 0, 9, typeof (0 he will not calculate the result, so NaN is not a number
after adding parentheses, it will first calculate, typeof (9 Infinity 0, and then typeof Infinity is Number
see MDN description
Key description on MDN (clasp): the
typeof operator returns a string indicating the type of uncalculated Operand.
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