Uncover five mysteries of JS caching mechanism

Revealed: Five mysteries of JS caching mechanism, specific code examples are required

Introduction:
When developing front-end web applications, we often encounter data Problems such as slow loading and freezing. In order to optimize the user experience and improve the loading performance of web pages, we can use JavaScript's caching mechanism. This article will reveal the five mysteries of the JS caching mechanism, along with specific code examples to help developers better understand and apply them.

1. HTTP caching mechanism
HTTP caching is one of the most commonly used caching mechanisms in web development. It uses the browser's cache to store static resources in web pages, such as images, style sheets, and script files. When the browser requests the same resource again, it reads it from the cache first instead of downloading it directly from the server.

In order to implement HTTP caching, the server will set fields such as Cache-Control and Expires in the response header. Specific code examples are as follows:

// Cache-Control设置缓存策略为public，表示所有用户（包括代理服务器）都可以缓存该资源
response.setHeader('Cache-Control', 'public');

// 设置缓存过期时间为1小时（以秒为单位）
response.setHeader('Expires', new Date(Date.now() + 3600000).toUTCString());

2. LocalStorage cache
localStorage is a client-side storage solution provided by HTML5, which can save key-value pair data locally in the browser. Using localStorage to cache data can reduce network requests and improve application response speed.

The following is a sample code using localStorage cache:

// 将数据保存到localStorage中
localStorage.setItem('data', JSON.stringify(data));

// 从localStorage中读取数据
const cachedData = JSON.parse(localStorage.getItem('data'));

3. sessionStorage cache
sessionStorage is also a client storage solution provided by HTML5. It is similar to localStorage, but it saves The data is only valid during the current session. When the browser window is closed, the data in sessionStorage will be cleared.

The following is a code example for sessionStorage cache:

// 将数据保存到sessionStorage中
sessionStorage.setItem('data', JSON.stringify(data));

// 从sessionStorage中读取数据
const cachedData = JSON.parse(sessionStorage.getItem('data'));

4. Service Worker cache
Service Worker is a JavaScript script running environment provided by the browser that is independent of the web page and can intercept the network Request and cache the response. Using Service Worker caching, we can implement offline browsing functionality and provide a better user experience.

The following is a code example that uses Service Worker to cache static resources:

// 注册Service Worker
navigator.serviceWorker.register('sw.js').then(registration => {
  console.log('Service Worker 注册成功！');
}).catch(error => {
  console.error('Service Worker 注册失败：', error);
});

// 缓存静态资源
self.addEventListener('install', event => {
  event.waitUntil(
    caches.open('my-cache').then(cache => {
      return cache.addAll([
        '/',
        '/index.html',
        '/style.css',
        '/script.js',
        '/image.png'
      ]);
    })
  );
});

// 从缓存中读取资源
self.addEventListener('fetch', event => {
  event.respondWith(
    caches.match(event.request).then(response => {
      return response || fetch(event.request);
    })
  );
});

5. Memoization (memory)
Memoization is an optimization technology that caches the calculation results of functions. Improve performance. It is suitable for functions with the same input and the same output. By caching the results of the function, repeated calculations can be avoided and the execution efficiency of the function can be improved.

The following is a sample code using Memoization:

// 缓存函数的计算结果
const memoize = fn => {
  const cache = new Map();
  return function(...args) {
    const key = JSON.stringify(args);
    if (cache.has(key)) {
      return cache.get(key);
    }
    const result = fn.apply(this, args);
    cache.set(key, result);
    return result;
  };
};

// 计算斐波那契数列
const fibonacci = memoize(n => {
  if (n <= 1) {
    return n;
  }
  return fibonacci(n - 1) + fibonacci(n - 2);
});

Conclusion:
The above are the five mysteries of the JS caching mechanism and specific code examples. By rationally utilizing the caching mechanism, we can greatly improve the loading performance and user experience of web pages. I hope this article can help developers better understand and apply caching technology and optimize front-end development work.

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