Execute the function as soon as the variable is declared

Currently, I am immersed in a project that involves a significant amount of user-generated code (influenced by this video ). My objective is to evaluate a portion of user-input code using eval(), and trigger a function every time a variable is defined, two variables are multiplied, or any other specific action takes place.

Is it feasible to accomplish this task using JavaScript?

One potential approach could involve scanning the input for instances of "var ...", analyzing what follows, and then performing the necessary actions. However, for various reasons, I would prefer to handle this process more legitimately by directly responding to code execution events.

javascriptevaluser-inputuser-defined-functions

Answer №1

For certain versions of Javascript, you have the option to utilize the Intercession API (also known as proxies) to redefine how objects mutate by writing your own code.

If that approach is not feasible, and you know the variable names in advance, you can employ setters, getters, or a polyfill like Object.watch for achieving similar results.

If you are unsure about the variable names beforehand, it is recommended to run the user-defined Javascript through a parser such as Esprima to obtain an AST. This allows you to insert arbitrary syntax directly into the AST when variables are defined (or hoisted), and then compile it back into functional code. Look for JSON objects with "type": "VariableDeclaration".

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