有没有比下面的pausecomp函数(取自此处)更好的方法来设计JavaScript中的睡眠?

function pausecomp(millis)
{
    var date = new Date();
    var curDate = null;
    do { curDate = new Date(); }
    while(curDate-date < millis);
}

这不是JavaScript中的Sleep的重复-动作之间的延迟;我希望在函数的中间有一个真正的睡眠,而不是在代码执行之前有一段延迟。


当前回答

或者只创建一个:

function yourFunction(){

   // Do something
   setInterval(myFunc(), 1000);
   // Do something else
}

function myFunc(){
   return;
}

这将只等待指定的时间间隔并调用函数,而该函数将不执行任何操作。

其他回答

这会帮你的。

var reloadAfter = 10; //seconds
var intervalId = setTimeout(function() {
    //code you want to execute after the time waiting
}, reloadAfter * 1000); // 60000 = 60 sec = 1 min

首先,应该使用setTimeout和setInterval,因为JavaScript具有回调性质。如果您想使用sleep(),则是控制流或代码架构不正确。

尽管如此,我想我仍然可以帮助实现两个睡眠。

1.我头顶上的假同步跑步:

// A module to do that //dual-license: MIT or WTF [you can use it anyhow and leave my nickname in a comment if you want to]
var _ = (function(){
  var queue = [];
  var play = function(){
    var go = queue.shift();
      if(go) {
        if(go.a) {
          go.f();
          play();
        }
        else
        {
          setTimeout(play, go.t);
        }
      }
  }
  return {
    go:function(f){
      queue.push({a:1, f:f});
    },
    sleep:function(t){
      queue.push({a:0, t:t});
    },
    playback:play
  }
})();

[也可以自动播放]

// Usage

_.go(function(){

  // Your code
  console.log('first');

});

_.sleep(5000);

_.go(function(){

  // Your code
  console.log('next');

});

// This triggers the simulation
_.playback();

2.实际同步运行

有一天,我对它进行了很多思考,我在JavaScript中真正睡觉的唯一想法就是技术。

睡眠函数必须是同步Ajax调用,超时设置为睡眠值。这就是真正睡觉的唯一方法。

如果您想休眠一个匿名函数,就像您创建的处理程序一样,我建议您使用以下方法:

function()
{
    if (!wait_condition)
    {
        setTimeout(arguments.callee, 100, /* Comma-separated arguments here */);
    }
    // The rest of the function
}

这段代码表示“如果等待条件尚未满足,请使用这些参数再次调用此函数。”。

拥抱JavaScript的异步特性!

以下所有内容都将立即返回,但只有一个地方可以放置发生事件后要运行的代码。

我在这里概述的方法都适用于不同的用例,并根据其复杂性大致排序。

不同之处如下:

等待某些条件变为现实在调用单个回调之前,等待一组方法完成(按任何顺序)在调用回调之前,以特定顺序运行一系列具有共享状态的异步方法

Wait

如果没有任何可访问的回调来告诉您什么时候完成了执行,那么等待某个条件是否为真是非常有用的。

这是一个非常基本的实现,它假设条件在某个时刻变为真。通过一些调整,它可以扩展到更有用(例如,通过设置呼叫限制)。(我昨天才写了这篇!)

function waitFor(predicate, successCallback) {
    setTimeout(function () {
        var result = predicate();
        if (result !== undefined)
            successCallback(result);
        else
            waitFor(predicate, successCallback);
    }, 100);
}

呼叫代码:

beforeEach(function (done) {
    selectListField('A field');

    waitFor(function () {
        var availableOptions = stores.scrapeStore(optionStore);
        if (availableOptions.length !== 0)
            return availableOptions;
    }, done);
});

在这里,我调用了加载ExtJS“store”的东西,并等待该存储包含一些东西后再继续(beforeEach是Jasmine测试框架的东西)。

等待几件事完成

我还需要在加载完不同的方法后运行一个回调。你可以这样做:

createWaitRunner = function (completionCallback) {
    var callback = completionCallback;
    var completionRecord = [];
    var elements = 0;

    function maybeFinish() {
        var done = completionRecord.every(function (element) {
            return element === true
        });

        if (done)
            callback();
    }

    return {
        getNotifier: function (func) {
            func = func || function (){};

            var index = elements++;
            completionRecord[index] = false;

            return function () {
                func.applyTo(arguments);
                completionRecord[index] = true;
                maybeFinish();
            }
        }
    }
};

呼叫代码:

var waiter = createWaitRunner(done);

filterList.bindStore = waiter.getNotifier();
includeGrid.reconfigure = waiter.getNotifier(function (store) {
    includeStore = store;
});

excludeGrid.reconfigure = waiter.getNotifier(function (store) {
    excludeStore = store;
});

您可以只等待通知,也可以包装使用传递给函数的值的其他函数。调用所有方法后,将运行done。

按顺序运行异步方法

当我在一行中调用一系列异步方法时(同样在测试中),我使用了不同的方法。这有点类似于您可以在Async库中得到的东西——series也做了同样的事情,我先读了一下这个库,看看它是否符合我的要求。我认为我的测试有一个更好的API(实现起来很有趣!)。

// Provides a context for running asynchronous methods synchronously
// The context just provides a way of sharing bits of state
// Use 'run' to execute the methods.  These should be methods that take a callback and optionally the context as arguments
// Note the callback is provided first, so you have the option of just partially applying your function to the arguments you want
// instead of having to wrap even simple functions in another function

// When adding steps you can supply either just a function or a variable name and a function
// If you supply a variable name then the output of the function (which should be passed into the callback) will be written to the context
createSynchronisedRunner = function (doneFunction) {
    var context = {};

    var currentPosition = 0;
    var steps = [];

    // This is the loop. It is triggered again when each method finishes
    var runNext = function () {
        var step = steps[currentPosition];
        step.func.call(null,
                       function (output) {
                           step.outputHandler(output);
                           currentPosition++;

                           if (currentPosition === steps.length)
                               return;

                           runNext();
                       }, context);
    };

    var api = {};

    api.addStep = function (firstArg, secondArg) {
        var assignOutput;
        var func;

        // Overloads
        if (secondArg === undefined) {
            assignOutput = function () {
            };
            func = firstArg;
        }
        else {
            var propertyName = firstArg;
            assignOutput = function (output) {
                context[propertyName] = output;
            };
            func = secondArg;
        }

        steps.push({
            func: func,
            outputHandler: assignOutput
        });
    };

    api.run = function (completedAllCallback) {
        completedAllCallback = completedAllCallback || function(){};

        var lastStep = steps[steps.length - 1];
        var currentHandler = lastStep.outputHandler;
        lastStep.outputHandler = function (output) {
            currentHandler(output);
            completedAllCallback(context);
            doneFunction();
        };

        runNext();
    };

    // This is to support more flexible use where you use a done function in a different scope to initialisation
    // For example, the done of a test but create in a beforeEach
    api.setDoneCallback = function (done) {
        doneFunction = done;
    };

    return api;
};

呼叫代码:

beforeAll(function (done) {
    var runner = createSynchronisedRunner(done);
    runner.addStep('attachmentInformation', testEventService.getAttachmentCalled.partiallyApplyTo('cat eating lots of memory.jpg'));
    runner.addStep('attachment', getAttachment.partiallyApplyTo("cat eating lots of memory.jpg"));
    runner.addStep('noAttachment', getAttachment.partiallyApplyTo("somethingElse.jpg"));
    runner.run(function (context) {
        attachment = context.attachment;
        noAttachment = context.noAttachment;
    });
});

这里的PartiallyApplyTo基本上是Douglas Crockford实现Curry的重命名版本。我正在处理的很多东西都将回调作为最后的参数,这样简单的调用就可以这样完成,而不必用一个额外的函数来包装一切。

我相信有一百万种方法可以做得更好,但我想我可以通过创建一个对象来尝试一下:

// execute code consecutively with delays (blocking/non-blocking internally)
function timed_functions()
{
    this.myfuncs = [];
    this.myfuncs_delays = []; // mirrors keys of myfuncs -- values stored are custom delays, or -1 for use default
    this.myfuncs_count = 0; // increment by 1 whenever we add a function
    this.myfuncs_prev    = -1; // previous index in array
    this.myfuncs_cur    = 0; // current index in array
    this.myfuncs_next  = 0; // next index in array
    this.delay_cur     = 0; // current delay in ms
    this.delay_default = 0; // default delay in ms
    this.loop = false;      // will this object continue to execute when at end of myfuncs array?
    this.finished = false;  // are we there yet?
    this.blocking = true;   // wait till code completes before firing timer?
    this.destroy = false;   // <advanced> destroy self when finished


    this.next_cycle = function() {
        var that  = this;
        var mytimer = this.delay_default;

        if(this.myfuncs_cur > -1)
            if(this.myfuncs_delays[this.myfuncs_cur] > -1)
                mytimer = this.myfuncs_delays[this.myfuncs_cur];

        console.log("fnc:" + this.myfuncs_cur);
        console.log("timer:" + mytimer);
        console.log("custom delay:" + this.myfuncs_delays[this.myfuncs_cur]);
        setTimeout(function() {
        // Time is up! Next cycle...
        that.cycle();

    }, mytimer);
}

this.cycle = function() {

    // Now check how far we are along our queue.. is this the last function?
    if(this.myfuncs_next + 1 > this.myfuncs_count)
    {
        if(this.loop)
        {
            console.log('looping..');
            this.myfuncs_next = 0;
        }
        else
            this.finished = true;
    }

    // First check if object isn't finished
    if(this.finished)
        return false;

    // HANDLE NON BLOCKING //
    if(this.blocking != true) // Blocking disabled
    {
        console.log("NOT BLOCKING");
        this.next_cycle();
    }

    // Set prev = current, and current to next, and next to new next
    this.myfuncs_prev = this.myfuncs_cur;
    this.myfuncs_cur  = this.myfuncs_next;
    this.myfuncs_next++;

    // Execute current slot
    this.myfuncs[this.myfuncs_cur]();

    // HANDLE BLOCKING
    if(this.blocking == true)  // Blocking enabled
    {
        console.log("BLOCKING");
        this.next_cycle();
    }

    return true;
};

// Adders
this.add = {
    that:this,

    fnc: function(aFunction) {
        // Add to the function array
        var cur_key = this.that.myfuncs_count++;
        this.that.myfuncs[cur_key] = aFunction;
        // Add to the delay reference array
        this.that.myfuncs_delays[cur_key] = -1;
    }
}; // end::this.add

// setters
this.set = {
    that:this,

    delay: function(ms) {
        var cur_key = this.that.myfuncs_count - 1;
        // This will handle the custom delay array this.that.myfunc_delays
        // Add a custom delay to your function container

        console.log("setting custom delay. key: "+ cur_key + " msecs: " + ms);
        if(cur_key > -1)
        {
            this.that.myfuncs_delays[cur_key] = ms;
        }
        // So now we create an entry on the delay variable
    },

    delay_cur:      function(ms) { this.that.delay_cur = ms; },
    delay_default:  function(ms) { this.that.delay_default = ms; },
    loop_on:        function()   { this.that.loop = true; },
    loop_off:       function()   { this.that.loop = false; },
    blocking_on:    function()   { this.that.blocking = true; },
    blocking_off:   function()   { this.that.blocking = false; },

    finished:            function(aBool) { this.that.finished = true; }
}; // end::this.set


// Setters
this.get = {
    that:this,

    delay_default: function() { return this.that.delay_default; },
    delay_cur:     function() { return this.that.delay_cur; }
    }; // end::this.get

} // end:::function timed_functions()

使用方式如下:

// // // BEGIN :: TEST // // //

// Initialize
var fncTimer = new timed_functions;

// Set some defaults
fncTimer.set.delay_default(1000);
fncTimer.set.blocking_on();
// fncTimer.set.loop_on();
// fncTimer.set.loop_off();


// BEGIN :: ADD FUNCTIONS (they will fire off in order)
fncTimer.add.fnc(function() {
    console.log('plan a (2 secs)');
});
fncTimer.set.delay(2000); // Set a custom delay for previously added function

fncTimer.add.fnc(function() {
    console.log('hello world (delay 3 seconds)');
});
fncTimer.set.delay(3000);

fncTimer.add.fnc(function() {
    console.log('wait 4 seconds...');
});
fncTimer.set.delay(4000);

fncTimer.add.fnc(function() {
    console.log('wait 2 seconds');
});
fncTimer.set.delay(2000);

fncTimer.add.fnc(function() {
    console.log('finished.');
});
// END :: ADD FUNCTIONS


// NOW RUN
fncTimer.cycle(); // Begin execution


// // // END :: TEST // // //