JS_GetNaNValue 编辑

Get the not-a-number (NaN) floating-point number as a value of type JS::Value.

Syntax

// Added in SpiderMonkey 42
JS::Value
JS_GetNaNValue(JSContext *cx);

// Obsolete since SpiderMonkey 42
jsval
JS_GetNaNValue(JSContext *cx);

Description

JS_GetNaNValue returns a value of type JS::Value that represents an IEEE floating-point quiet Not-a-Number (NaN).

NaN is typically used in JavaScript as the return value of a numeric operation when an argument is invalid or conversion fails. For example, 0/0 and Math.sqrt(-1) both return NaN. So do Number("xyzzy") and Math.sin("Frank"). While the IEEE standard defines many NaN bit-patterns, they are indistinguishable in JavaScript, so in effect there's only one NaN.

NaN is not equal to any other value. In fact, it is not even equal to itself: if x is NaN, then x != x.

See Also

• MXR ID Search for JS_GetNaNValue
• JS_GetNegativeInfinityValue
• JS_GetPositiveInfinityValue
• bug 1184564 -- Changed jsval to JS::Value