Metaprogramming uses code to automate code or alter code behavior. It treats code as data, enabling repetitive work and orthogonal concerns such as logging, tracing, and performance tracking to be inserted programmatically. section 7.0
JavaScript supports both static and dynamic approaches. Symbols provide unique properties and hooks for fundamental operations, while Proxy and Reflect weave behavior into objects at runtime without polluting their interfaces. section 7.8 section 7.0
Common metaprogramming mechanisms include:
- Symbols create collision-free properties and can influence iteration, primitive conversion, spreading, and printing. section 7.8 section 7.0
- Proxy and Reflect dynamically weave behavior into an object's runtime representation. section 7.8
- Method decorators modularize cross-cutting behavior and reduce duplicated implementation. section 7.8
A practical use
An application can weave logging, tracing, or performance metrics into existing behavior while keeping those concerns separate from the object's primary interface. section 7.0 section 1.0
