Chapter The Lifecycle Crisis-JS Tutorial-php.cn

Chapter The Lifecycle Crisis

Chapter 1: The Lifecycle Crisis

The alarm rang in Arin’s ears as she stumbled into Sector 7. Hours earlier, she was in the training room, practicing drills under Captain Lifecycle's watchful eye. Now, chaos descended—no simulations, no preparation.

“Cadet Arin, over here!” Lieutenant Stateflow called. Arin wove her way past crates and other members of the Planetary Defense Corps (PDC), joining her squad, The Web Accidents.

"Look alive, Web Accidents! They’re coming!" Captain Lifecycle yelled. Arin looked up to see The Bug Horde—flickering, dark shapes advancing through the sky. At the rear loomed Queen Glitch, a larger shadow spreading across the horizon.

Arin steadied herself, gripped her staff, and focused. Today, she had to learn—and fast.

“The Product Lifecycle Mishap”

As The Bug Horde approached, Arin recalled the issue uncovered earlier—the Products Module, a mess of chaotic connections. The original code haunted her:

The Original Code

import { useEffect, useState } from 'react';

function Products({ items, category, fetchProducts }) {
  const [processedItems, setProcessedItems] = useState([]);
  const [fullName, setFullName] = useState("");

  // Overdoing data transformations in useEffect
  useEffect(() => {
    const filteredItems = items.filter(item => item.category === category);
    setProcessedItems(filteredItems);
  }, [items, category]);

  // Misusing useEffect for derived state
  useEffect(() => {
    setFullName(`${category} Products`);
  }, [category]);

  // Using useEffect for API calls
  useEffect(() => {
    fetchProducts(); 
  }, [category]);

  return (
    <div>
      <h1>{fullName}</h1>
      {processedItems.map(product => (
        <div key={product.id}>
          <p>{product.name}</p>
        </div>
      ))}
    </div>
  );
}

Copy after login

Every change in items or category caused a cascade of updates and glitches—like the multiplying bugs attacking them. "Cadet, remember!" Captain Lifecycle's voice cut through her thoughts. "You must understand the flow—control it, don’t just react!"

“Step 1: Handling Data Transformations”

Captain Lifecycle moved beside Arin. “Each swing, Cadet—make it efficient, make it count.”

Arin recalled the chaotic filtering logic:

useEffect(() => {
  const filteredItems = items.filter(item => item.category === category);
  setProcessedItems(filteredItems);
}, [items, category]);

Copy after login

The constant filtering caused redundant updates. The solution lay in efficiency.

The Refactor: Use useMemo to Optimize Data Transformation

const processedItems = useMemo(() => {
  return items.filter(item => item.category === category);
}, [items, category]);

Copy after login

She swung her staff deliberately, making each movement precise. Just like reducing redundant renders with useMemo, each of her strikes needed purpose.

“Step 2: Managing Derived State”

Arin moved alongside Render the Shapeshifter, who adapted fluidly to the bugs. “Don’t overthink, Cadet—keep it direct,” Render said, morphing to deflect an attack.

Arin thought about the overly complex logic in the module:

const [fullName, setFullName] = useState("");
useEffect(() => {
  setFullName(`${category} Products`);
}, [category]);

Copy after login

Recalculating this simple value felt chaotic—like the disordered battlefield. She needed simplicity.

The Refactor: Direct Computation for Derived State

import { useEffect, useState } from 'react';

function Products({ items, category, fetchProducts }) {
  const [processedItems, setProcessedItems] = useState([]);
  const [fullName, setFullName] = useState("");

  // Overdoing data transformations in useEffect
  useEffect(() => {
    const filteredItems = items.filter(item => item.category === category);
    setProcessedItems(filteredItems);
  }, [items, category]);

  // Misusing useEffect for derived state
  useEffect(() => {
    setFullName(`${category} Products`);
  }, [category]);

  // Using useEffect for API calls
  useEffect(() => {
    fetchProducts(); 
  }, [category]);

  return (
    <div>
      <h1>{fullName}</h1>
      {processedItems.map(product => (
        <div key={product.id}>
          <p>{product.name}</p>
        </div>
      ))}
    </div>
  );
}

Copy after login

Arin adjusted her stance, making her actions direct and streamlined, just like simplifying derived state computations. Each swing was precise, cutting down the bugs more effectively.

“Step 3: Handling External Threats”

Suddenly, the ground shook. Arin looked up at Queen Glitch, a dark force distorting everything around her. “She’s targeting the core!” Lieutenant Stateflow shouted. “Contain the external threat!”

Arin recalled the flawed approach to managing external API calls in the Products Module:

useEffect(() => {
  const filteredItems = items.filter(item => item.category === category);
  setProcessedItems(filteredItems);
}, [items, category]);

Copy after login

Uncontrolled API calls mirrored the instability in front of her—reacting without strategy. The answer lay in deliberate action.

The Refactor: Proper Use of useEffect for External Interactions

const processedItems = useMemo(() => {
  return items.filter(item => item.category === category);
}, [items, category]);

Copy after login

Arin steadied herself, realizing the importance of focusing on what mattered—making interactions count. She synched her energy with the flow of the battle, each move deliberate, like properly managed API calls to stabilize the core.

The Learning and the Calm

The sun dipped below the horizon, and the Bug Horde retreated. Queen Glitch vanished like a dark cloud lifting. Exhausted, Arin fell to one knee, breathing heavily.

Lieutenant Stateflow approached, nodding at her. “You learned to adapt today, Cadet. You made each action matter.”

Captain Lifecycle joined them. “This was the first step, Arin. Lifecycle stability isn’t a one-time battle—it’s continuous.”

Arin stood, her body aching but her understanding deepened. Today’s mission wasn’t just about defeating bugs—it was about stabilizing the flow and understanding deliberate action. Each lesson from the Products Module mirrored the fight here—cutting through chaos, making every effect meaningful, every dependency clear.

She looked at the sky, where Queen Glitch had vanished, and knew her journey had only begun. Planet Codex needed stability, and Arin was ready to learn, adapt, and defend.

Cheatsheet: Lessons from "The Lifecycle Crisis"

Scenario	Initial Misstep	Refactored Approach	Why It's Better
Data Transformation	useEffect with setState to transform data	useMemo for transforming data	Avoids unnecessary re-renders by recomputing only when dependencies change, improving efficiency and reducing bugs.
Derived State from Props	useState and useEffect to calculate derived state	Direct computation in the component	Simplifies the code, reduces complexity, and ensures better maintainability without extra state or re-renders.
Fetching External Data	useEffect without managing dependencies well	useEffect with appropriate dependencies	Ensures API calls are only triggered when necessary, focusing on external interactions and improving performance.
Event Handling	Inside useEffect	Use direct event handlers	Keeps logic focused and avoids unnecessary complexity inside useEffect. Helps maintain clearer code and intended behaviors.
Managing Subscriptions	Forgetting cleanup	Always include cleanup in useEffect	Ensures that no memory leaks occur and resources are properly managed, leading to a stable component lifecycle.
Dependency Management	Over-complicating dependencies in useEffect	Thoughtful and minimal dependencies	Prevents unintended re-renders and helps maintain predictable behavior in components, resulting in a smoother experience.
Understanding Lifecycle	Mapping lifecycle methods directly from class-based components	Rethink with functional Hooks like useEffect, useMemo	Ensures that the functional components are optimized, taking advantage of the benefits of React Hooks, and reducing redundancy.

Scenario

Initial Misstep

Refactored Approach

Why It's Better

Data Transformation

useEffect with setState to transform data

useMemo for transforming data

Avoids unnecessary re-renders by recomputing only when dependencies change, improving efficiency and reducing bugs.

Derived State from Props

useState and useEffect to calculate derived state

Direct computation in the component

Simplifies the code, reduces complexity, and ensures better maintainability without extra state or re-renders.

Fetching External Data

useEffect without managing dependencies well

useEffect with appropriate dependencies

Ensures API calls are only triggered when necessary, focusing on external interactions and improving performance.

Event Handling

Inside useEffect

Use direct event handlers

Keeps logic focused and avoids unnecessary complexity inside useEffect. Helps maintain clearer code and intended behaviors.

Managing Subscriptions

Forgetting cleanup

Always include cleanup in useEffect

Ensures that no memory leaks occur and resources are properly managed, leading to a stable component lifecycle.

Dependency Management

Over-complicating dependencies in useEffect

Thoughtful and minimal dependencies

Prevents unintended re-renders and helps maintain predictable behavior in components, resulting in a smoother experience.

Understanding Lifecycle

Mapping lifecycle methods directly from class-based components

Rethink with functional Hooks like useEffect, useMemo

Ensures that the functional components are optimized, taking advantage of the benefits of React Hooks, and reducing redundancy.

Key Takeaways:

Make Every Action Deliberate: Like Arin’s battle, each piece of code should have a clear purpose. Avoid redundant operations.
Use useMemo for Data Transformations: Recompute transformations only when necessary. Focus on efficient actions.
Simplify Derived State: Compute directly where possible—reduce complexity and keep logic clear.
Use useEffect for External Interactions: Connect to external dependencies, not internal logic. Manage dependencies carefully to avoid unwanted side effects.
Always Clean Up Effects: Ensure cleanup to prevent memory leaks.
Hooks Aren’t Lifecycle Methods: Rethink functionality in a functional context instead of direct mapping.

Remember: Just like Arin, mastering useEffect is about balancing effort, adaptation, and deliberate focus to maintain stability. Keep it precise, and keep @learning!

The above is the detailed content of Chapter The Lifecycle Crisis. For more information, please follow other related articles on the PHP Chinese website!