Type Definition jscjs_sys::api::JSObjectHasInstanceCallback

type JSObjectHasInstanceCallback = Option<unsafe extern "C" fn(ctx: JSContextRef, constructor: JSObjectRef, possibleInstance: JSValueRef, exception: *mut JSValueRef) -> bool>;

@typedef JSObjectHasInstanceCallback @abstract hasInstance The callback invoked when an object is used as the target of an ‘instanceof’ expression. @param ctx The execution context to use. @param constructor The JSObject that is the target of the ‘instanceof’ expression. @param possibleInstance The JSValue being tested to determine if it is an instance of constructor. @param exception A pointer to a JSValueRef in which to return an exception, if any. @result true if possibleInstance is an instance of constructor, otherwise false. @discussion If you named your function HasInstance, you would declare it like this:

bool HasInstance(JSContextRef ctx, JSObjectRef constructor, JSValueRef possibleInstance, JSValueRef* exception);

If your callback were invoked by the JavaScript expression ‘someValue instanceof myObject’, constructor would be set to myObject and possibleInstance would be set to someValue.

If this callback is NULL, ‘instanceof’ expressions that target your object will return false.

Standard JavaScript practice calls for objects that implement the callAsConstructor callback to implement the hasInstance callback as well.