Introduction to Workers 970
Comparing Workers and Threads 970
Types of Workers 971
 Dedicated Web Worker 971
 Shared Web Worker 971
 Service Worker 971
The WorkerGlobalScope 971
 WorkerGlobalScope Properties and Methods 972
 Subclasses of WorkerGlobalScope 972
Dedicated Workers 973
Dedicated Worker Basics 973
 Creating a Dedicated Worker 973
 Worker Security Restrictions 974
 Using the Worker Object 975
 The DedicatedWorkerGlobalScope 976
Dedicated Workers and Implicit MessagePorts 976
Understanding the Dedicated Worker Lifecycle 977
Configuring Worker Options 979
Creating a Worker from Inline JavaScript 979
Dynamic Script Execution Inside a Worker 980
Delegating Tasks to Subworkers 982
Handling Worker Errors 983
Communicating with a Dedicated Worker 983
 Communicating with postMessage() 983
 Communicating with MessageChannel 984
 Communicating with BroadcastChannel 986
Worker Data Transfer 987
 Structured Clone Algorithm 987
 Transferable Objects 988
 SharedArrayBuffer 990
Worker Pools 993
Shared Workers 997
Shared Worker Basics 997
 Creating a Shared Worker 997
 SharedWorker Identity and Single Occupancy 998
 Using the SharedWorker Object 999
 The SharedWorkerGlobalScope 999
Understanding the Shared Worker Lifecycle 1000
Connecting to a Shared Worker 1001
Service Workers 1003
Service Worker Basics 1003
 The ServiceWorkerContainer 1004
 Creating a Service Worker 1004
 Using the ServiceWorkerContainer Object 1005
 Using the ServiceWorkerRegistration Object 1006
 Using the ServiceWorker Object 1007
 Service Worker Security Restrictions 1008
 The ServiceWorkerGlobalScope 1008
 Service Worker Scope Limitations 1010
The Service Worker Cache 1012
 The CacheStorage Object 1013
 The Cache Object 1014
 Maximum Cache Storage 1017
Service Worker Clients 1017
Service Workers and Consistency 1018
Understanding the Service Worker Lifecycle 1019
 The Parsed State 1020
 The Installing State 1020
 The Installed State 1021
 The Activating State 1022
 The Activated State 1023
 The Redundant State 1024
 Updating a Service Worker 1024
Inversion of Control and Service Worker Persistence 1024
Managing Service Worker File Caching with updateViaCache 1025
Forced Service Worker Operation 1025
Service Worker Messaging 1026
Intercepting a fetch Event 1028
 Return from Network 1028
 Return from Cache 1029
 Return from Network with Cache Fallback 1029
 Return from Cache with Network Fallback 1029
 Generic Fallback 1029
Push Notifications 1030
 Displaying Notifications 1030
 Handling Notification Events 1031
 Subscribing to Push Events 1031
 Handling Push Events 1032
Summary 1033

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Ultimately, most developers will find that service workers are most useful for two primary tasks: acting as a caching layer for network requests, and enabling push notifications. In this sense, the service worker is a tool designed to enable web pages to behave like native applications.