Request Interceptors in JavaScript

// Basic interceptor pattern
const originalFetch = window.fetch

window.fetch = async function(...args) {
  console.log('Request:', args)
  
  const response = await originalFetch(...args)
  
  console.log('Response:', response)
  
  return response
}

// Request/Response interceptor class
class FetchInterceptor {
  constructor() {
    this.requestInterceptors = []
    this.responseInterceptors = []
  }
  
  addRequestInterceptor(fn) {
    this.requestInterceptors.push(fn)
  }
  
  addResponseInterceptor(fn) {
    this.responseInterceptors.push(fn)
  }
  
  async fetch(url, options = {}) {
    // Run request interceptors
    let modifiedOptions = options
    for (const interceptor of this.requestInterceptors) {
      modifiedOptions = await interceptor(url, modifiedOptions)
    }
    
    let response = await fetch(url, modifiedOptions)
    
    // Run response interceptors
    for (const interceptor of this.responseInterceptors) {
      response = await interceptor(response)
    }
    
    return response
  }
}