Starting from a simple script language in a web browser, JavaScript is now one of the most extensively used programming languages and evolves fast. At the same time, JavaScript is also notorious for its dynamic and complex semantics. To understand the semantics of JavaScript rigorously, developers and researchers should refer to the language specification named ECMA-262. However, since ECMA-262 is written imperatively, even the proficient readers suffer from understanding it. To mitigate this problem, we present an automatic approach to derive an ECMA-262 double debugger that breaks down barriers between ECMA-262 and its readers. Our approach is two-fold: (1) to compile ECMA-262 to an executable program in IRES (2) to extend an interpreter of IRES to an ECMA-262 double debugger.