Explain the use of proxies in JavaScript for state management and reactivity systems.

Proxies in JavaScript are used in state management and reactivity systems to intercept and customize interactions with objects such as property accesses and mutations.

This enables automatic detection of changes and triggers reactive updates without manual event handling. Proxies allow features like validation, computed properties, and listeners for state changes, offering a lightweight and flexible way to build reactive state systems.

Code

const state = new Proxy({ count: 0 }, {
  get(target, prop) {
    console.log(`Accessing ${prop}`);
    return target[prop];
  },
  set(target, prop, value) {
    console.log(`Updating ${prop} to ${value}`);
    target[prop] = value;
    // trigger UI update here
    return true;
  }
});
state.count;     // Logs: Accessing count
state.count = 5; // Logs: Updating count to 5