Proxy Pattern

This teaches you how to use JavaScript's Proxy object to intercept and control operations on objects like property access, assignment, and function calls. It's from patterns.dev and covers the fundamentals with the person object example, showing how to add validation, logging, and access control through get and set traps. The guide includes practical advice on using Reflect for cleaner code and is honest about the tradeoffs: proxies add overhead and shouldn't be used in performance critical paths. Good for learning when you actually need this pattern versus just using regular getters and setters. The validation examples are straightforward and the "when NOT to use" section is refreshingly direct about avoiding overengineering.

skills.sh installs: 627
GitHub stars: 258
last updated: Aug 21, 2026

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Install

$ npx -y skills add patternsdev/skills --skill proxy-pattern --agent claude-code

Installs into .claude/skills of the current project.

Files

Proxy Pattern

With a Proxy object, we get more control over the interactions with certain objects. A proxy object can determine the behavior whenever we're interacting with the object, for example when we're getting a value, or setting a value.

When to Use

Use this when you need to add validation, formatting, notifications, or debugging to object access
This is helpful for controlling and intercepting property gets and sets on objects

When NOT to Use

In performance-critical hot paths where Proxy overhead on every property access matters
When simple getter/setter methods or Object.defineProperty achieve the same validation with less indirection
When the target objects are rarely accessed and the interception logic isn't needed

Instructions

Create a Proxy with a handler object defining get and set traps
Use the Reflect object within handlers for cleaner property access and modification
Add validation logic in the set trap to ensure data integrity
Avoid using proxies in performance-critical code paths as they add overhead