JavaScript Proxy and Handler

In JavaScript, a Proxy is an object that wraps another object and intercepts its operations, allowing you to customize its behavior. This is done through a handler object that defines traps — methods to intercept fundamental operations such as property access, assignment, function calls, etc.

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Syntax

• targetObject: The original object to wrap.
• handlerObject: Defines traps to intercept operations on the target.

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Example 1: Basic Proxy with get Trap

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Common Handler Traps

• get: Intercepts property access.
• set: Intercepts property assignment.
• apply: Intercepts function calls.
• deleteProperty: Intercepts property deletion.
• has: Intercepts the in operator.
• ownKeys: Intercepts Object.keys(), Object.getOwnPropertyNames(), etc.

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Example 2: set Trap for Validation

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Example 3: Proxy for Logging

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Example 4: Function Proxy using apply Trap

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Key Takeaways

• Proxy allows intercepting and redefining fundamental operations on objects and functions.
• The handler object contains traps that customize behavior.
• Common use cases include validation, logging, security, lazy loading, and building frameworks.
• Proxies can wrap both objects and functions.
• Proxies enable meta-programming by modifying behavior at runtime.