Skip to main content

Cache API in JavaScript

Learn how to cache resources with Cache API in JavaScript.

Cache API Cheat-sheet
The Cache API allows Service Workers to have a control over resources(HTML pages, CSS, JavaScript files, images, JSON, etc) to be cached. Through Cache API a Service Worker can cache resources for offline and retrieve them later.
Detecting the cache support
Check if the caches object available in window.
let isCacheSupported = 'caches' in window;
caches is an instance of CacheStorage .
Creating/Initialize Cache
We can create a cache with name using open method, which will returns a promise . If the cache already exists , then it don’t create a new cache.
caches.open('cacheName').then( cache => {
});
You cannot you cannot access caches set up for others origin(domain).
The cache which you’r are creating will be created for your domain.
You can add multiple cache for same domain, which you can access by caches.keys()
Adding an item to cache
You can cache a resource using three methods add , addAll , set . add() and addAll() method automatically fetches a resource, and caches it, whereas in set method we will fetch a data and set the cache.
1.add
let cacheName = 'userSettings'; 
let url = '/api/get/usersettings';
caches.open(cacheName).then( cache => {
   cache.add(url).then( () => {
       console.log("Data cached ")
    });
});
In thee above code, internally a request for /api/get/usersettings url is sent to server, once the data is received, the response will be cached.
2.addAll
addAll accepts an array of URL , and returns a promise when all the resources are cached.
let urls = ['/get/userSettings?userId=1', '/get/userDetails'];
caches.open(cacheName).then( cache => {
cache.addAll(urls).then( () => {
       console.log("Data cached ")
    });
});
Cache.add/Cache.addAll do not cache responses with Response.status values that are not in the 200 range, Cache.put lets you store any request/response pair.
3. put
put adds a key/value pairs to current Cache object.In put we need to manually fetch the request and set the value.
Note: put() will overwrite any key/value pair previously stored in the cache that matches the request.
let cacheName = 'userSettings';
let url = '/api/get/userSettings';
fetch(url).then(res => {
  return caches.open(cacheName).then(cache => {
    return cache.put(url, res);
  })
})
Retrieving from a cache
Using cache.match() you can get the Response that was stored to the URL .
const cacheName = 'userSettings'
const url = '/api/get/userSettings'
caches.open(cacheName).then(cache => {
  cache.match(url).then(settings => {
    console.log(settings);
  }
});
The settings is a Response Object, which looks like
Response {
  body: (...),
  bodyUsed: false,
  headers: Headers,
  ok: true,
  status: 200,
  statusText: "OK",
  type: "basic",
  url: "https://test.com/api/get/userSettings"
}
Retrieve All Items in the Cache
The cache object contains keys methods which will have all the url of the current cache object.
caches.open(cacheName).then( (cache) => { 
  cache.keys().then( (arrayOfRequest) => { 
      console.log(arrayOfRequest); // [Request,  Request]
  });
});
arrayOfRequest is an array of Request objects, which has all details about the request.
Retrieving all caches
caches.keys().then(keys => {
  // keys is an array with the list of keys
})
Remove an item from the cache
You can use delete method on cache object to remove a particular cached Request.
let cacheName = userSettings; 
let urlToDelete = '/api/get/userSettings';
caches.open(cacheName).then(cache => {
  cache.delete(urlToDelete)
})
Remove the cache completely
caches.delete(cacheName).then(() => {
   console.log('Cache successfully deleted!');
})

Comments

Post a Comment

Popular posts from this blog

Understand Angular’s forRoot and forChild

  forRoot   /   forChild   is a pattern for singleton services that most of us know from routing. Routing is actually the main use case for it and as it is not commonly used outside of it, I wouldn’t be surprised if most Angular developers haven’t given it a second thought. However, as the official Angular documentation puts it: “Understanding how  forRoot()  works to make sure a service is a singleton will inform your development at a deeper level.” So let’s go. Providers & Injectors Angular comes with a dependency injection (DI) mechanism. When a component depends on a service, you don’t manually create an instance of the service. You  inject  the service and the dependency injection system takes care of providing an instance. import { Component, OnInit } from '@angular/core'; import { TestService } from 'src/app/services/test.service'; @Component({ selector: 'app-test', templateUrl: './test.component.html', styleUrls: ['./test.compon...
Post a Comment
Read more

How to use Ngx-Charts in Angular ?

Charts helps us to visualize large amount of data in an easy to understand and interactive way. This helps businesses to grow more by taking important decisions from the data. For example, e-commerce can have charts or reports for product sales, with various categories like product type, year, etc. In angular, we have various charting libraries to create charts.  Ngx-charts  is one of them. Check out the list of  best angular chart libraries .  In this article, we will see data visualization with ngx-charts and how to use ngx-charts in angular application ? We will see, How to install ngx-charts in angular ? Create a vertical bar chart Create a pie chart, advanced pie chart and pie chart grid Introduction ngx-charts  is an open-source and declarative charting framework for angular2+. It is maintained by  Swimlane . It is using Angular to render and animate the SVG elements with all of its binding and speed goodness and uses d3 for the excellent math functio...
Post a Comment
Read more

How to solve Puppeteer TimeoutError: Navigation timeout of 30000 ms exceeded

During the automation of multiple tasks on my job and personal projects, i decided to move on  Puppeteer  instead of the old school PhantomJS. One of the most usual problems with pages that contain a lot of content, because of the ads, images etc. is the load time, an exception is thrown (specifically the TimeoutError) after a page takes more than 30000ms (30 seconds) to load totally. To solve this problem, you will have 2 options, either to increase this timeout in the configuration or remove it at all. Personally, i prefer to remove the limit as i know that the pages that i work with will end up loading someday. In this article, i'll explain you briefly 2 ways to bypass this limitation. A. Globally on the tab The option that i prefer, as i browse multiple pages in the same tab, is to remove the timeout limit on the tab that i use to browse. For example, to remove the limit you should add: await page . setDefaultNavigationTimeout ( 0 ) ;  COPY SNIPPET The setDefaultNav...
Post a Comment
Read more