A JavaScript program may be represented in an intermediate form to be executed by a JavaScript interpreter. A browser may be configured to intercept JavaScript code and pass execution control to a Java-based interpreter engine. The instructions are converted by a representation generator component of the engine into an intermediate representation equivalent using the Java programming language. The representation scheme may be suitable for execution by a stack-machine implemented interpreter. The representation scheme may use Java classes and objects, and create logical commands representing the JavaScript program. The intermediate representation may be stored as Java objects in a stack data structure. The stack data structure may be constructed from an array of elements, where each element is either an operator or an operand, and where each element derives from an abstract Java class with generic functionality and each element contains data relating to the operator or data type it represents.