Angular HTTP ETag

Tested: IE 9+; Edge 13; Chrome 29, 50+; Firefox 46+; Safari 7+; iOS 9.2+; Android 4.4, 5.1.

Easy ETag-based caching for $http service requests! Increase responsiveness, decrease bandwidth usage.

• Caches ETag headers and sends them back to the server in the If-None-Match header.
• Caches response data with flexible cache configuration.
• Support for $cacheFactory, sessionStorage, and localStorage caches out-of-the-box.
• Easily adaptable for other third-party cache services.
• Compatible with AngularJS 1.2–1.6.

Example Usage:

angular
  .module('myApp', [
    'http-etag'
  ])
  .config(function (httpEtagProvider) {
    httpEtagProvider
      .defineCache('persistentCache', {
        cacheService: 'localStorage'
      })
  })

  .controller('MyCtrl', function ($http) {
    var self = this

    $http
      .get('/my_data.json', {
        etagCache: 'persistentCache'
      })
      .then(function success (response, itemCache) {
        var data = response.data
        // Modify the data from the server
        data._fullName = data.first_name + ' ' + data.last_name
        // Update the cache with the modified data
        itemCache.set(data)
        // Assign to controller property
        self.fullName = data._fullName
      }, function error (response) {
        if (response.status != 304) alert('Request error')
      })
      // Synchronous method called if request was previously cached
      // status == 'cached'; headers === undefined;
      .ifCached(function (response, itemCache) {
        self.fullName = data._fullName
      })
  })

Need more information on how ETags work? Read this.

Detailed Documentation

• Service Provider
• Service
• $http Decorator
• Cache Service Adapters

Quick Guide

Install Module

$ npm install angular-http-etag

Or download from master/release

Include Dependency

Include 'http-etag' in your module's dependencies.

// The node module exports the string 'http-etag'...
angular.module('myApp', [
  require('angular-http-etag')
])

// ... otherwise, include the code first then the module name
angular.module('myApp', [
  'http-etag'
])

Define Caches

.config(function ('httpEtagProvider') {
  httpEtagProvider
    .defineCache('persistentCache', {
      cacheService: 'localStorage'
    })
    .defineCache('sessionCache', {
      cacheService: 'sessionStorage'
    })
    .defineCache('memoryCache', {
      cacheService: '$cacheFactory',
      cacheOptions: {
        number: 50 // LRU cache
      },
      deepCopy: true // $cacheFactory copies by reference by default
    })
})

If you so desire, you can define your own caches. The default cache uses $cacheFactory and is limited to 25 cache items (Least Recently Used algorithm).

Define the caches you'd like to use by using defineCache(cacheId[, config]), passing a cache ID followed by the cache configuration. The configuration you pass will extend the default configuration, which can be set using the setDefaultCacheConfig(config) method. If you don't pass a config, a new cache will be defined using the default config.

See more in the Service Provider documentation.

Cache Requests

Using the default cache with default configuration and an automatically generated cache itemKey based on the request:

$http.get('/data', {
    etagCache: true
  })
  .then(responseHandler)
  .ifCached(responseHandler)

function responseHandler (response, itemCache) {
  // Differentiating between cached and successful request responses
  var isCached = response.status === 'cached'

  // itemCache is a cache object bound to the cache item associated with this request.
  itemCache.info()
  // { id: 'httpEtagCache',
  //   itemKey: '/data',
  //   deepCopy: false,
  //   cacheResponseData: true,
  //   cacheService: '$cacheFactory',
  //   cacheOptions: { number: 25 } }
}

Using a defined cache from the previous section and an automatically generated cache itemKey:

$http.get('/data', {
    etagCache: 'persistentCache'
  })
  .then(responseHandler)
  .ifCached(responseHandler)

function responseHandler (response, itemCache) {
  itemCache.info()
  // { id: 'persistentCache',
  //   itemKey: '/data',
  //   deepCopy: false,
  //   cacheResponseData: true,
  //   cacheService: 'localStorage',
  //   cacheOptions: { number: 25 } }
}

Using a defined cache and a specified key for the cache item:

$http.get('/data', {
    etagCache: {
      id: 'persistentCache',
      itemKey: 'whatFineKeyYouHave'
    }
  })
  .then(responseHandler)
  .ifCached(responseHandler)

function responseHandler (response, itemCache) {
  itemCache.info()
  // { id: 'persistentCache',
  //   itemKey: 'whatFineKeyYouHave',
  //   deepCopy: false,
  //   cacheResponseData: true,
  //   cacheService: 'localStorage',
  //   cacheOptions: { number: 25 } }
}

The etagCache property also accepts a function that returns on of the values demonstrated; a boolean, a string, or an object.

See more in the $http Decorator and Service documentation.

Contributing

Write an issue. Then, possibly, hopefully...

1. Fork the repo.
2. Make a branch.
3. Write the code.
4. Write the tests.
5. Run tests. (npm test)
6. Open a pull request.