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JavaScriptProxyReflectMetaprogramming

JavaScript Proxy and Reflect API

Master JavaScript Proxy and Reflect. From basic traps to reactive programming to validation patterns.

B
Bootspring Team
Engineering
July 16, 2020
7 min read

Proxy enables custom behavior for fundamental operations. Here's how to use it effectively.

Basic Proxy

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Common Traps

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Validation

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Reactive Programming

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Default Values

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Access Control

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Function Proxies

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Array Proxy

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Reflect API

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Best Practices

Design: ✓ Use Reflect for default behavior ✓ Always return from set trap ✓ Preserve prototype chain ✓ Handle all edge cases Performance: ✓ Avoid proxying hot paths ✓ Cache proxy instances ✓ Minimize trap operations ✓ Profile performance impact Patterns: ✓ Validation and type checking ✓ Change detection/reactivity ✓ Access control ✓ Logging and debugging Avoid: ✗ Overusing proxies ✗ Forgetting receiver argument ✗ Breaking invariants ✗ Circular proxy chains

Conclusion

Proxy and Reflect enable powerful metaprogramming in JavaScript. Use them for validation, reactivity, access control, and function decoration. Always use Reflect for default behavior and be mindful of performance implications.

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