js-typeof-soruce

typeof.c

  JS_PUBLIC_API(JSType)
    JS_TypeOfValue(JSContext *cx, jsval v)
    {
        JSType type = JSTYPE_VOID;
        JSObject *obj;
        JSObjectOps *ops;
        JSClass *clasp;

        CHECK_REQUEST(cx);
        if (JSVAL_IS_VOID(v)) {  // (1)
            type = JSTYPE_VOID;
        } else if (JSVAL_IS_OBJECT(v)) {  // (2)
            obj = JSVAL_TO_OBJECT(v);
            if (obj &&
                (ops = obj->map->ops,
                 ops == &js_ObjectOps
                 ? (clasp = OBJ_GET_CLASS(cx, obj),
                    clasp->call || clasp == &js_FunctionClass) // (3,4)
                 : ops->call != 0)) {  // (3)
                type = JSTYPE_FUNCTION;
            } else {
                type = JSTYPE_OBJECT;
            }
        } else if (JSVAL_IS_NUMBER(v)) {
            type = JSTYPE_NUMBER;
        } else if (JSVAL_IS_STRING(v)) {
            type = JSTYPE_STRING;
        } else if (JSVAL_IS_BOOLEAN(v)) {
            type = JSTYPE_BOOLEAN;
        }
        return type;
    }