如何暂停网络工作者

Question

我试图查看网络工作者文档，虽然我没有找到我要找的东西，但文档也不是很好，所以我想我只是问问它。

我正在使用与外部设备对话的 Cordova 开发移动应用程序。我需要每秒向外部设备发送一些命令。为此，我设置了 Web Workers，它基本上相当于 JS 中的线程。但是有一个命令，要工作，必须转弯外部设备。也就是说，如果设备在尝试处理它时收到任何其他命令，该命令将失败。为此，我只想暂停我的线程。

在 Java 中这很容易，有一个 public void thread.suspend()，然后是 thread.resume()。我的自然倾向是 Web Workers 会将此作为默认功能。 Worker.suspend(), worker.resume()，但我找不到任何文档支持 Workers 拥有这个想法，尽管这是对多线程的普遍期望。有没有这样的固有功能？如果没有，是否有实现类似功能的最佳实践？

Answer 1

此代码段展示了如何

创建三个 web worker
从网络工作者那里获取计数器值
暂停网络工作者
检测所有三个 web worker 何时停止
重启网络工作者

由于 Whosebug 片段的限制，网络工作者代码是内联的。

function getInlineJS() {
    var js = $('[type="javascript/worker"]').text();
    var blob = new Blob([js], {"type": "text/plain"});
    return URL.createObjectURL(blob);
}

var worker_list = [];
var worker_num = 3;
var pause_count = null;

function create_workers() {
    var index;
    for (index = 0; index < worker_num; index++) {
        var web_worker = new Worker(getInlineJS());
        var counter_selector = '#counter' + (index + 1);
        (function(selector) {
            web_worker.onmessage = function(event) {
                var paused = event.data['paused'];
                if (paused) {
                    pause_count++;
                }
                if (pause_count == worker_num) {
                    // At this point we know the workers have all stopped
                    $('#pause_count').text(pause_count);
                }
                var counter = event.data['counter'];
                $(selector).text(counter);
            }
        })(counter_selector);
        worker_list.push(web_worker);
    }
}

/**
 * Send a bogus message to get the workers to send their counters
 */
function update_counters() {
    var index;
    for (index = 0; index < worker_num; index++) {
        var message = {'index': index};
        worker_list[index].postMessage(message);
    }
}

/**
 * Send the pause flag to the workers
 * @param pause_state
 */
function pause_counters(pause_state) {
    var index;
    for (index = 0; index < worker_num; index++) {
        var message = {'pause_flag': pause_state};
        worker_list[index].postMessage(message);
    }
}

var pause_state = false;
$(document).ready(function() {
    create_workers();
    setInterval(update_counters, 1000);
    $('#pause').on('click', function() {
        pause_state = !pause_state;
        if (pause_state) {
            pause_count = 0;
        }
        else {
            $('#pause_count').text('');
        }
        pause_counters(pause_state);
        $('#pause').text(pause_state ? 'Start' : 'Stop');
    });
});

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Web Worker</title>
</head>
<body>
    <div class="counter">
        Counter 1: <span id="counter1"></span>
    </div>
    <div class="counter">
        Counter 2: <span id="counter2"></span>
    </div>
    <div class="counter">
        Counter 3: <span id="counter3"></span>
    </div>
    <div class="button">
        <button id="pause" type="button">Stop</button>
    </div>
    <div>
        Pause Count: <span id="pause_count"></span>
    </div>
</body>
<script src="https://code.jquery.com/jquery-3.1.1.js"
        integrity="sha256-16cdPddA6VdVInumRGo6IbivbERE8p7CQR3HzTBuELA="
        crossorigin="anonymous"></script>
<script src="sync.js"></script>
<script type="javascript/worker">
var pause_flag = false;
var counter = 0;

function run_command() {
    if (!pause_flag) {
        counter++;
    }
}

var interval = setInterval(run_command, 1000);

onmessage = function(event) {
    if ('pause_flag' in event.data) {
        pause_flag = event.data['pause_flag'];
    }
    var message = {
        "paused": pause_flag,
        "counter": counter
    };
    postMessage(message);
};
</script>
</html>

如何暂停网络工作者

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