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JSCache Pro

Advanced JavaScript Caching Analysis & Optimization Tool

Cache Header Analysis Performance Test Bundle Analysis

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Or upload your JavaScript files

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Test Results

Cache Visualization

Optimization Tips

Analyzing JavaScript caching configuration...

JavaScript Caching Analysis Results

Cache Efficiency Score

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Overall caching effectiveness

Potential Bandwidth Savings

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Reduction in data transfer

Cache Hit Ratio

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Percentage of cached requests

Load Time Improvement

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Faster page loads with caching

Detailed JavaScript Cache Analysis

Cache-Control Header

Presence and configuration of Cache-Control directives for JS files

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ETag Implementation

Effective use of ETags for cache validation

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File Versioning

Use of cache busting techniques for updated files

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CDN Utilization

Effective use of CDN for JavaScript delivery

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JavaScript Cache Visualization

Browser Cache Usage

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Percentage of JS files served from browser cache

CDN Cache Effectiveness

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Effectiveness of CDN caching for JavaScript files

Cache Distribution by JavaScript Type

Vendor Libraries

Cache effectiveness for third-party libraries

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Application Code

Cache effectiveness for your application code

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Framework Code

Cache effectiveness for framework code (React, Vue, etc.)

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JavaScript Caching Optimization Recommendations

Implement Long-Term Caching for Vendor Libraries

Third-party libraries rarely change and should be cached aggressively with long max-age values. Use content hashing for cache busting.

# Nginx configuration for JavaScript caching
location ~* \.(js)$ {
    expires 1y;
    add_header Cache-Control "public, immutable";
    add_header Access-Control-Allow-Origin "*";
}

Use Code Splitting and Dynamic Imports

Split your JavaScript into smaller chunks and load them on demand. This reduces initial bundle size and improves caching effectiveness.

// Dynamic import example
const loadModule = async () => {
  const module = await import('./module.js');
  module.init();
};

Implement Service Workers for Advanced Caching

Use service workers to cache JavaScript files and serve them from cache even when offline or with poor connectivity.

// Service worker caching example
self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open('js-cache-v1').then((cache) => {
      return cache.addAll([
        '/js/main.js',
        '/js/vendor.js',
        '/js/runtime.js'
      ]);
    })
  );
});

Optimal Cache Header Configurations

Vendor Libraries (React, Vue, etc.)

Cache for 1 year with immutable directive

Cache-Control: public, max-age=31536000, immutable

Application Code

Cache for 1 week with content-based versioning

Cache-Control: public, max-age=604800

Dynamic JavaScript

Cache for 1 hour with validation or use no-cache

Cache-Control: public, max-age=3600, must-revalidate

Why JavaScript Caching Matters

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Faster Page Loads

Cached JavaScript files load instantly from local storage instead of requiring network requests, significantly improving page load times and Time to Interactive.

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Reduced Server Load

Effective caching reduces the number of requests to your origin server, allowing it to handle more traffic with the same resources.

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Lower Bandwidth Costs

By serving cached JavaScript files, you reduce bandwidth consumption, which can significantly lower hosting costs, especially for high-traffic sites.

Frequently Asked Questions

How does JavaScript caching improve website performance? +

JavaScript caching significantly improves website performance in several ways:

• Faster Load Times: Cached JS files load from local storage instead of over the network, reducing latency
• Reduced Network Requests: Fewer HTTP requests mean faster page rendering and less server load
• Improved Time to Interactive: Pages become interactive faster when JavaScript is cached
• Better User Experience: Faster loading leads to lower bounce rates and higher engagement
• Reduced Bandwidth Usage: Less data transfer benefits both website owners and users, especially on mobile networks

Studies show that effective caching can improve page load times by 30-50% for returning visitors, making it one of the most impactful performance optimizations.

What's the difference between memory cache and disk cache? +

Browsers use two types of caching for JavaScript files:

• Memory Cache:
  • Stored in RAM for fastest access
  • Volatile - cleared when browser is closed
  • Used for resources loaded during the current session
  • Extremely fast but limited capacity
• Disk Cache:
  • Stored on the hard drive
  • Persistent - remains after browser restart
  • Used for resources with long cache durations
  • Slower than memory but much larger capacity

Browsers automatically determine which cache to use based on resource size, frequency of access, and cache headers. Frequently accessed JavaScript files are often kept in memory cache for fastest access.

How can I implement effective cache busting for JavaScript? +

Cache busting ensures users get the latest version of your JavaScript files. Here are the most effective techniques:

• Filename Versioning: Change the filename when content changes (e.g., app.a1b2c3.js)
• Query String Parameter: Add a version parameter (e.g., app.js?v=1.2.3)
• Content Hash: Generate hash based on file content (e.g., app.abc123.js)
• Build Tools: Use Webpack, Rollup, or Parcel to automate cache busting

The most reliable method is content-based hashing, where the filename changes only when the file content changes. This allows for long cache times while ensuring updates are immediately available.

// Webpack configuration for content hashing
module.exports = {
  output: {
    filename: '[name].[contenthash].js',
    chunkFilename: '[name].[contenthash].chunk.js'
  }
};

Should I use a CDN for JavaScript files? +

Using a CDN for JavaScript files provides several benefits:

• Faster Delivery: Files are served from locations closer to your users
• Better Caching: CDNs have sophisticated caching mechanisms
• Reduced Server Load: Offloads traffic from your origin server
• Improved Reliability: CDNs provide redundancy and failover
• HTTP/2 and Brotli Support: Most CDNs support modern protocols and compression

For third-party libraries, using CDNs like cdnjs, jsDelivr, or unpkg is recommended as many users may already have these files cached from other websites. For your own JavaScript files, consider using a CDN if you have a global audience or high traffic volumes.

When using a CDN, ensure proper cache headers are set and implement fallbacks in case the CDN is unavailable.

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