JS_DefaultValue 编辑

Obsolete since JSAPI 44
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

This article covers features introduced in SpiderMonkey 1.8.6

Converts a JavaScript object to a primitive value, using the semantics of that object's internal [[DefaultValue]] hook.

Renamed to JS::ToPrimitive from JSAPI 44.

Syntax

bool
JS_DefaultValue(JSContext *cx, JS::Handle<JSObject*> obj, JSType hint,
                JS::MutableHandle<JS::Value> vp);

Description

JS_DefaultValue converts a JavaScript object, obj, to a primitive value using that object's [[DefaultValue]] hook. ECMAScript specifies that all objects have a [[DefaultValue]] hook. Objects with classes defined by ECMAScript itself all use the [[DefaultValue]] algorithm specified in §8.12.8 (but note the algorithm's special case for Date objects). Objects with a custom JSClass specified by the embedder will invoke that class's convert hook, which must convert the object to a primitive value, to determine the primitive result of conversion. Behavior when the convert hook is JS_ConvertStub is identical to that for objects defined by ECMAScript.

On success, JS_DefaultValue stores the converted value in *vp and returns true. On error or exception, it returns false, and the value left in *vp is undefined.

See Also

• MXR ID Search for JS_DefaultValue
• JS::ToPrimitive
• bug 1054756 - renamed to JS::ToPrimitive