How to handle dependencies array for custom hooks in react

In React, custom Hooks often utilize dependency arrays similarly to built-in Hooks like useEffect, useMemo, and useCallback. A dependency array is a mechanism that signals React when to recompute or trigger specific operations. The handling of dependency arrays in custom Hooks follows the same principles as in built-in Hooks.

If your custom Hook internally uses Hooks such as useEffect, useMemo, or useCallback, adhere to these guidelines for dependency management:

1. Include only necessary dependencies: The dependency array should contain all variables that influence the Hook's execution or output. If a value remains unchanged during the Hook's execution or its change does not affect the output, exclude it from the array.

2. Ensure dependency stability: If an object or function in the dependency array creates a new reference on every render, it may cause the effect or compute function to re-execute even if the value hasn't changed. To prevent this, wrap the dependency with useMemo to memoize computed results or useCallback to memoize functions, ensuring their references remain stable across renders.

3. Handle dependencies for functions and objects: When the dependency is a function or object, wrap it with useCallback or useMemo to avoid unnecessary side effects or computations triggered by component re-renders.

4. Use an empty dependency array for one-time execution: To execute logic only once during component mount, pass an empty array [] as the dependency.

For example, consider a custom Hook using useState and useEffect:

jsx
import { useState, useEffect } from 'react';

function useCustomHook(dependency) {
  const [state, setState] = useState(null);

  useEffect(() => {
    // Code that executes only when dependency changes
    const doSomething = () => {
      // Operation based on dependency
      console.log(dependency);
    };

    doSomething();

    // Optional cleanup function
    return () => {
      // Cleanup logic
    };
  }, [dependency]); // Dependency array includes dependency

  return state;
}

In this example, useEffect depends on the external variable dependency, so it is included in the dependency array. Whenever dependency changes, useEffect re-executes.

In summary, handling dependency arrays in custom Hooks focuses on identifying values or references that may change during execution and affect the output or side effects. These should be included in the dependency array.