React 與 React Native 的差異

1. 平台/目標不同

• React 主要用來開發「網頁」應用，將 UI 元件轉換為 HTML 標籤，運作於各種瀏覽器。

• React Native 則讓你用 JavaScript 開發「行動裝置原生應用」，元件最後渲染為 iOS/Android 裡的原生 UI 控件，不經過瀏覽器12345。

2. 使用的組件不同

• React 組件就是 HTML 元素（如 <div>、<button>），結合 CSS、JS 一起打造 UI。

• React Native 沒有 HTML，改用 <View>（類似 <div>）、<Text>、<Image> 這些專屬於原生平台的元素，並以 JavaScript 對應原生實體145。

3. 樣式設定與佈局

• React 使用 CSS/CSS-in-JS 等樣式方案。

• React Native 則用類似 JS 物件描述的「StyleSheet」語法，支援 Flexbox，無法直接用 CSS 或動畫庫45。

4. 渲染機制與效能

• React 透過虛擬 DOM 比對與 HTML 更新，來加快 DOM 操作。

• React Native 的組件經由 JS 與原生程式間的「橋接層」（bridge），將 UI 直接生成原生元件，實現近原生的行動體驗35。

5. 開發與測試環境

• React 主打網頁開發、可用 Chrome DevTools 等瀏覽器工具除錯。

• React Native 需用 Xcode/Android Studio 配合行動模擬器或真機測試，另有專用的 DevTools 與熱重載工具45。

總結

• React：適用「桌面/行動網頁」前端開發，專注於網頁技術（HTML、CSS、JS）。

• React Native：專為「行動裝置原生 App」打造，共享 React 的開發理念，但渲染「原生 UI」，可跨平台（iOS/Android）共用邏輯與部分 UI 組件。

兩者核心思想相似（組件化、狀態管理、宣告式 UI），但應用範疇、渲染方式和開發流程皆大不相同。如果目標是「網頁」→ React；若需「原生行動 App」→ React Native13456。

TypeScript 檔案副檔名 .ts 與 .tsx 差異

在 TypeScript 專案開發中，常見兩種副檔名：.ts 和 .tsx。它們的差異主要體現在是否支援 JSX 語法、以及實際應用場景上：

實例解析

• .ts 範例（無 JSX）：

  typescript
  // utils.ts
  export function add(a: number, b: number): number {
    return a + b;
  }
  

• .tsx 範例（有 JSX）：

  typescript
  // MyComponent.tsx
  import React from 'react';
  interface Props { name: string }
  const MyComponent: React.FC<Props> = ({ name }) => (
    <div>Hello, {name}!</div>
  );
  

核心結論

• 只要檔案內有 JSX 語法（通常為 React 元件），副檔名就必須用 .tsx。純程式邏輯、工具函式、型別宣告等，不涉及 JSX 的檔案則維持用 .ts12345。

• 使用正確副檔名，可讓 TypeScript 編譯器正確理解、檢查語法，有助於專案維護與錯誤預防。

判斷方式：「有沒有用到 JSX？」有 → .tsx；沒有 → .ts67。

這也是 TypeScript 結合 React 時，專案結構乾淨且效率高的關鍵慣例。

Difference Between .ts and .tsx

What You Cannot Use With .ts

If you use .ts instead of .tsx, you cannot:

• Write JSX syntax:
  For example, the following will result in a compile error in .ts files:

  typescript
  // Won't work in .ts file:
  const el = <div>Hello World</div>;
  

  TypeScript only allows this syntax in files with the .tsx extension.

• Define React component UI directly in code:
  You can't include code such as:

  typescript
  export const MyComponent = () => <span>Hi</span>;
  

  All UI definitions using JSX must be in .tsx files.

• Mix TS logic with markup in the same file:
  If your logic returns JSX, use .tsx.
  Pure logic, types, or utility functions without JSX should remain .ts.

How to Decide

• Use .tsx if: Your file contains JSX markup or React component UIs.

• Use .ts if: Your file is TypeScript logic, types, config, or functions and does not use JSX.

Summary:
Choosing .ts for files with JSX will cause compilation errors. JSX syntax is only allowed in .tsx files, so any React component with UI markup must use .tsx. All other TypeScript files without JSX should use .ts for clarity and best practices.

Node.js is a free, open-source, cross-platform JavaScript runtime environment that allows developers to run JavaScript code outside of a web browser, most commonly on servers or command-line tools168. Instead of being a language or a framework, Node.js provides an environment for executing JavaScript, enabling the development of servers, web apps, APIs, command line tools, and scripts157.

Key aspects of Node.js include:

• JavaScript on the Server: Node.js lets developers use JavaScript for server-side programming, unifying back-end and front-end development around a single language678.

• Built on V8 Engine: It runs on Google's V8 JavaScript engine (the same as Chrome), which compiles JavaScript to fast, efficient machine code67.

• Event-Driven & Non-Blocking: Node.js uses an event-driven, non-blocking I/O model. Instead of relying on threads or blocking execution while waiting for input/output operations (like reading files or handling network requests), Node.js can handle many connections concurrently using callbacks and an internal event loop. This design makes it lightweight and highly scalable, ideal for real-time and data-intensive applications3678.

• Rich Standard Library & Ecosystem: Node.js comes with built-in modules for HTTP, file system access, streams, and more, and it has a vast ecosystem of additional packages through npm67.

• Cross-Platform: Node.js runs on multiple platforms, including Windows, macOS, Linux, and more18.

• Not a Framework: While sometimes confused for one, Node.js is not a web framework like Express or Koa; these are built on top of Node.js7.

Typical Use Cases:

• Developing web servers and REST APIs.

• Building real-time applications (like chat apps).

• Command-line tools.

• Scripts and automation.

In summary, Node.js lets you use JavaScript for everything from server-side applications to command line tools, with a fast, scalable, and non-blocking architecture1678.

How to Use Zustand to Set and Get Variables Across Different Files

Zustand is a simple and lightweight state management library for React applications, which allows you to create centralized stores that can be accessed and modified across various components or files.

To set and get a variable (state) across different files using Zustand, follow these key steps:

1. Create a Zustand Store in a Separate File

Create a dedicated store file (for example, store.js or useStore.js) where you define your state variables and actions using the create function from Zustand.

javascript
// store.js
import create from 'zustand';

const useStore = create((set) => ({
  myVariable: 0,            // State variable
  setMyVariable: (value) => set({ myVariable: value }),  // Action to set the variable
  incrementVariable: () => set((state) => ({ myVariable: state.myVariable + 1 })), // Another action example
}));

export default useStore;

2. Import and Use the Store in Other Files/Components

You can then import the Zustand store hook wherever you need to access or manipulate the state.

javascript
// In a React component or any other JavaScript file

import useStore from './store';

function ComponentA() {
  const myVariable = useStore((state) => state.myVariable);
  const setMyVariable = useStore((state) => state.setMyVariable);

  return (
    <div>
      <div>Value: {myVariable}</div>
      <button onClick={() => setMyVariable(myVariable + 1)}>Increase</button>
    </div>
  );
}

3. Access Zustand State Outside React Components (If Needed)

Zustand provides .getState() and .setState() on the store, which allow you to access or update the state outside React components or hooks, for example, in utility functions or other stores.

javascript
import useStore from './store';

// Get current state value
const currentValue = useStore.getState().myVariable;

// Set a new state value
useStore.setState({ myVariable: 10 });

Summary Table of Key Usage Patterns

Best Practices

• Single source of truth: Keep your global state centralized in one or a few store files.

• Use the store hook inside React components: Use the hook (useStore) to subscribe and automatically update UI on state changes.

• Use .getState() and .setState() for non-React contexts: These are useful for integration, testing, or cross-store interactions.

• Modular stores: You can create multiple stores for different domains and even access one store inside another if needed.

By following the above approach, you can cleanly and efficiently set and get variables across different files using Zustand in your React projects.

If you'd like, I can also provide a more concrete example tailored to your specific use case. Just ask!

References:
1 Zustand State Management - DEV Community
2 Zustand get state from another Zustand store - Stack Overflow
3 Zustand, When, how and why - Dev.to
4 Zustand Key Features: State Management Simplified - CodeParrot
5 Zustand: Simplifying State Management in React E-commerce - Pedro Alonso Blog

Limitations of Calling and Using Hooks in React

Hooks in React (like useState, useEffect, and custom hooks such as Zustand's store hooks) provide a powerful and flexible way to manage state and lifecycle logic in functional components. However, there are several important limitations and rules governing how hooks must be called and used:

1. Only Call Hooks at the Top Level

• Hooks cannot be called inside loops, conditions, or nested functions.

  • Hooks must be called in the same order every time a component renders. Putting hooks inside conditional statements or loops breaks this rule and can cause unpredictable bugs.

Example (invalid):

javascript
if (isLoggedIn) {
  useEffect(() => { /* ... */ }, []);
}

This pattern is not allowed and will trigger errors.

2. Only Call Hooks from React Functions

Hooks can only be used:

• Inside React functional components

• Inside custom hooks

You cannot call hooks:

• From regular JavaScript functions

• From class components

• Outside of component or hook bodies (e.g., in event handlers, utility files outside React)

Example (valid):

javascript
function MyComponent() {
  useMyCustomHook();
  // ...
}

Example (invalid):

javascript
function notAComponent() {
  useState(); // ❌ This will not work
}

3. Hooks Are Not Available in Class Components

Hooks only work in function-based (functional) components. If you're using React class components, hooks cannot be used at all.

4. Rules of Custom Hooks

When you write your own custom hooks, all the above rules continue to apply. Your custom hooks should only call other hooks at the top level, and themselves only be called from React components or other hooks.

5. Cannot Use Hooks Conditionally

• You cannot call a hook conditionally within a component; all hooks need to be invoked in the same order on every render.

• Skipping or reordering hook calls (e.g., returning early before a hook is called) is not allowed.

6. No Async Hook Functions

Hook callbacks (like those passed to useEffect or useMemo) cannot themselves be declared async directly. You must handle asynchronous logic inside them, not on the function signature.

Summary Table

In short:
Hooks are powerful, but they come with strict rules—always call them at the top level of function components or custom hooks, never conditionally or inside regular JavaScript functions, and never from class components. This consistency is key for React to track state and lifecycle correctly, ensuring predictable and bug-free rendering.

Difference Between React and JavaScript

Overview

JavaScript is a fully-featured, high-level programming language essential for building interactive and dynamic websites and web applications.
React (or React.js) is a library built with JavaScript, designed specifically for constructing sophisticated, interactive user interfaces on the web.

Fundamental Comparison

Key Details

JavaScript

• Purpose: General-purpose scripting language used for adding logic, interactivity, and dynamic behavior to web pages.

• Where It Works: Browser, backend (Node.js), and many other environments.

• Direct DOM Manipulation: Updates elements and responds to events by changing the actual DOM tree.

• Flexibility: Can be used alone or with libraries/frameworks such as React, Angular, or Vue12.

React

• Purpose: Focuses on building complex, interactive, and large-scale user interfaces.

• Built On JavaScript: React code is written in JavaScript, often using additional JSX syntax (JavaScript XML) for describing UI elements concisely.

• Virtual DOM: React uses a virtual representation of the DOM. When data changes, it efficiently updates only the necessary parts of the real DOM, improving performance for dynamic UIs23.

• Component-Based: UI is developed as small, reusable components, enhancing maintainability and testability234.

• Declarative: Developers describe what the UI should look like for a given state, and React takes care of updating the UI when state changes.

• Requires Build Tools: Modern React apps often need tools like Babel and bundlers to translate JSX and ES6+ features into browser-compatible code5.

When to Use Which?

• Use JavaScript Alone: For small, simple scripts, adding dynamic features, or when minimal structure is required.

• Use React: For interactive, stateful, or large-scale applications requiring many UI updates, reusable UI elements, and a structured approach.

Analogy

• JavaScript is like the raw material (e.g., steel) for construction.

• React is like a set of blueprints and pre-made building blocks for quickly assembling complex structures using that material.

Summary

• JavaScript is the foundational language of web development.

• React leverages JavaScript to provide a streamlined, efficient way to build modern, interactive user interfaces with a component-based, declarative style523146.

You can distinguish between React functional components and regular JavaScript functions by looking at their purpose, what they return, and how they are used within your code.

Fundamental Differences

Examples

Regular JavaScript Function:

javascript
function add(a, b) {
  return a + b;
}

• Not intended for UI rendering.

• Returns a value, not JSX.

React Functional Component:

javascript
import React from 'react';

function Welcome(props) {
  return <h1>Hello, {props.name}!</h1>;
}

• Returns JSX (which React renders as UI).

• Designed to be used like <Welcome name="John" />.

Technical Details

• All React functional components are JavaScript functions, but not all JavaScript functions are React components. The distinction comes from:

  1. Returning JSX (or a React element), and

  2. Being used in the React component tree15.

• React components can be defined using either the function keyword or as arrow functions (with const), but they must always return something renderable (e.g., JSX or null)56.

• A regular function returning JSX does not “become” a component unless it's used as one (i.e., via <ComponentName /> syntax or React.createElement(ComponentName)) in React58.

Child Components Without Hooks

If a child component does not use any React hooks, it is still safe to use as a React functional component as long as it only returns JSX and is called as a React component within the React tree8.

• You do not need hooks for a function to be a valid React component—hooks are optional, used for managing state, side effects, refs, etc.

• The key is that the function returns JSX and is used in the React tree.

Potential issue:

• If you attempt to call a React component function directly (e.g., ChildComponent(props)) instead of using <ChildComponent {...props} />, you bypass React's lifecycle and hooks mechanism. This can lead to problems if hooks are used inside, but if the child component has no hooks, this pattern does not immediately break React's rules (though it is not recommended for clear code semantics)8.

Summary

• React functional components: Functions designed to return JSX and be rendered by React. They may or may not use hooks.

• Regular JS functions: Not intended for UI; do not take or return JSX.

• A child component with no hooks: Is still a valid React component and is safe to use as <ChildComponent />. Not using hooks does not affect validity; returning JSX does.

Key tip:
If a function returns JSX and is called as a React component in a render tree, it is a React functional component—regardless of whether it uses hooks158.