Infinity is some number in javascript?

问题

alert(1/0) alerts Infinity and alert(1/-0) alerts -Infinity. alert(-1/-0) alerts Infinity, as I could expect when doing some operations with real numbers. I can't say that infinity is a measurable value. Does javascript think it is some number?

回答1:

Yes, Infinity and -Infinity are special values of the Number type. From the ES5 spec:

There are two other special values, called positive Infinity and negative Infinity. For brevity, these values are also referred to for expository purposes by the symbols +∞ and −∞, respectively. (Note that these two infinite Number values are produced by the program expressions +Infinity (or simply Infinity) and -Infinity.)

Also note that NaN is a value of the Number type too, despite it being an acronym for "not a number".

回答2:

JavaScript uses IEEE-754 to represent numerical types; that specification includes values for non-numbers such as +/-Infinity and "NaN".

(1/0) // => Infinity
typeof(Infinity) // => "number"

Number.POSITIVE_INFINITY ===  Infinity // => true
Number.NEGATIVE_INFINITY === -Infinity // => true

Arithmetic and logical operations including the infinite values should behave as expected.

回答3:

From the Mozilla docs:

The initial value of Infinity is Number.POSITIVE_INFINITY. The value Infinity (positive infinity) is greater than any other number including itself. This value behaves mathematically like infinity; for example, any positive number multiplied by Infinity is Infinity, and anything divided by Infinity is 0.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity

来源：https://stackoverflow.com/questions/24166320/infinity-is-some-number-in-javascript