问题
I am a newcomer to Javascript and web programming in general. I am trying to figure out web workers, and have the following code (running in chrome):
worker_example.html
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript" src="worker_example.js"></script>
</head>
<html>
worker_example.js
var worker = new Worker("worker.js");
worker.addEventListener('message', function(e) {
document.write("hello");
}, false);
worker.postMessage("");
worker.js
// self.postMessage("");
My question is why doesn't worker.postMessage("") trigger the event? If I uncomment the single line in worker.js, however, everything works fine.
回答1:
The event listener attached to worker listens for messages coming from the worker to the parent page. You need to register a listener in the worker as well.
parent.js
var worker = new Worker('worker.js');
worker.addEventListener('message', function (e) {
console.log(e.data);
});
worker.postMessage('marco');
worker.js
self.addEventListener('message', function (e) {
self.postMessage(e.data + ' polo');
});
来源：https://stackoverflow.com/questions/14328826/javascript-web-workers-why-do-i-need-to-postmessage-twice-to-trigger-event