Understanding the Proxy Pattern
Use JavaScript’s Proxy to intercept and modify object interactions at runtime, letting you add control, lazy evaluation, or data transformations without touching the original code.
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Why this pattern matters
In real systems, our code often sits between what the client requests and what’s actually allowed or available.
For example, we might need to:
Delay connecting to a heavy database client until the first query.
Enforce permissions so some roles can’t call certain methods.
Log or shape data returned from an API without rewriting its logic.
Normally, that means cluttering our classes with if checks, “secure” wrappers, or special versions of objects. It works, but it spreads logic everywhere.
The Proxy Pattern gives us a cleaner mechanism: a programmable layer that controls how an object is accessed or used, without modifying the object itself. No subclassing, no patching, no re-exports. It’s a single invisible layer that enforces rules or optimizes behavior at runtime without touching the underlying code. This pattern isn’t just possible in JavaScript; it’s built right into the language through the native Proxy object.
How the pattern works
A Proxy acts as a stand-in for another object.
When we interact with the Proxy—by reading, writing, or calling a property—JavaScript routes that interaction through the Proxy’s handler. The handler can run custom logic, then decide whether to forward the operation to the original target object.
In JavaScript, this is powered by the built-in Proxy constructor, which takes two parts:
The target: The real object we want to guard or extend. ...