Lesson overview · Free interview practice

Meta-programming

Learn about Proxies and Reflect for dynamic programming.

Topics in the full lesson
  • Introduction to Meta-programming
  • Understanding Proxies
  • Intercepting Object Operations
  • Using the Reflect API
  • Practical Use Cases for Proxies
  • Best Practices
  • Exercises

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TheoryEasy

`Reflect` API as Default Trap Implementation

Question

How does the Reflect API relate to Proxy handler traps? Why is Reflect.get(target, key, receiver) preferred over target[key] inside a get trap?

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

`apply` and `construct` Traps

Question

How do the apply and construct traps work? Implement both: a logging wrapper for function calls and a logging wrapper for class instantiation.

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

`Proxy` and Handler Traps

Question

What is a Proxy in JavaScript? Show a Proxy intercepting get, set, and has with the handler trap pattern.

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

Practical Proxy Patterns Catalog

Question

What are the canonical practical uses of Proxy in JavaScript? Show code for four patterns.

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TheoryHard

Proxy Validator Pattern

Question

Implement a validation Proxy that enforces a schema on property assignments — types per key, no unknown keys. What does this beat compared to class getters/setters?

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Explain your reasoning or try an implementation before comparing answers.

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