JS_SetOperationCallback
syntax void js_setoperationcallback(jscontext *cx, jsoperationcallback callback); jsoperationcallback js_getoperationcallback(jscontext *cx); void js_triggeroperationcallback(jsruntime *rt); name type description cx jscontext * a context.
... callback jsoperationcallback (only in js_setoperationcallback) the callback function to install.
... callback syntax jsbool (*jsoperationcallback)(jscontext *cx); name type description cx jscontext * pointer to a jscontext in which this callback was installed.

JS_MaybeGC
calling js_maybegc periodically when the application is busy, from a jsbranchcallback or jsoperationcallback added in spidermonkey 1.8, can keep memory usage down and improve performance.