关于NaN的一个疑问？

Question

NaN，即非数值（Not a Number）是一个特殊的数值，这个数值用于表示一个本来要返回数值的操作数未返回数值的情况（这样就不会抛出错误了）。例如，在其他编程语言中，任何数值除以非数值都会导致错误，从而停止代码执行。但在ECMAScript中，任何数值除以非数值会返回NaN，其他数除以非数值会返回有符号的Infinity，因此不会影响其他代码的执行。 出自《高程三》

上述中斜体表述有什么问题吗？

Answer 1

我觉得是经过隐式转换之后还不能成为数字的就是NaN。

Answer 2

除法会先将操作数转换为数字，然后Applying the / Operator：

• If either operand isNaN, the result is NaN.
• The sign of the result is positive if both operands have the same sign, negative if the operands have different signs.
• Division of an infinity by an infinity results in NaN.
• Division of an infinity by a zero results in an infinity. The sign is determined by the rule already stated above.
• Division of an infinity by a nonzero finite value results in a signed infinity. The sign is determined by the rule already stated above.
• Division of a finite value by an infinity results in zero. The sign is determined by the rule already stated above.
• Division of a zero by a zero results in NaN; division of zero by any other finite value results in zero, with the sign determined by the rule already stated above.
• Division of a nonzero finite value by a zero results in a signed infinity. The sign is determined by the rule already stated above.
• In the remaining cases, where neither an infinity, nor a zero, norNaNis involved, the quotient is computed and rounded to the nearest representable value using IEEE 754-2008 round to nearest, ties to even mode. If the magnitude is too large to represent, the operation overflows; the result is then an infinity of appropriate sign. If the magnitude is too small to represent, the operation underflows and the result is a zero of the appropriate sign. The ECMAScript language requires support of gradual underflow as defined by IEEE 754-2008.