A method includes constructing a lambda object-oriented scripting language (λJS) model for a software program written in JavaScript; converting the λJS model to a continuation-passing style (CPS) model for the software program; constructing a control flow graph (CFG) for the software program based on the CPS model; and optimizing the CPS model by merging a sequence of two or more “let” operations. The two or more “let” operations in the CPS model and are generated based on the λJS model, so that they are represented by a single node in the CFG.