Worker - Githubissues

Why: JavaScript Concurrency， multi-threads
Types of web works: Dedicated Workers and Shared Workers.

Example:


// main script
<button onclick="sayHI()">Say HI</button>
<button onclick="unknownCmd()">Send unknown command</button>
<button onclick="stop()">Stop worker</button>
<output id="result"></output>

``` js
// doWork2.js
self.addEventListener('message', function(e) {
  var data = e.data;
  switch (data.cmd) {
    case 'start':
      self.postMessage('WORKER STARTED: ' + data.msg);
      break;
    case 'stop':
      self.postMessage('WORKER STOPPED: ' + data.msg +
                       '. (buttons will no longer work)');
      self.close(); // Terminates the worker.
      break;
    default:
      self.postMessage('Unknown command: ' + data.msg);
  };
}, false);

messages passed between main pages and workers are copied, not shared. Structured cloning is great, but a copy can take hundreds of milliseconds. To combat the perf hit, you can use Transferable Objects.

phymooc / learn-javascript

Worker #3

Service Worker

应用

生命周期