Metaprogramming in JavaScript encompasses techniques like reflection, dynamic property access, function manipulation, eval, proxy objects, prototype manipulation, decorators, and code generation.
In simple words, Meta-programming in JavaScript involves writing code that dynamically manipulates other code during runtime, enabling the creation of more flexible and dynamic programs by altering their behavior on-the-fly.
Reflection allows for the inspection and manipulation of object properties and methods. Dynamic property access permits runtime modification of object structures. Function manipulation leverages JavaScript's first-class functions for tasks like higher-order functions and closures, while eval executes code from strings, albeit with security concerns. Proxy objects intercept object operations for customization, prototype manipulation dynamically adjusts an object's prototype chain, and decorators annotate and modify class members at design time. Lastly, code generation dynamically produces JavaScript code, often utilized in templating engines.
Metaprogramming provides versatility but demands careful usage to maintain code clarity and security.