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

JavaScript函数不允许任何暂停。使用同步JavaScript,可以实现过程。过程等待I/O操作和睡眠超时。它可用于JavaScript 1.7。

演示:

演示睡眠演示可暂停程序

其他回答

我在JavaScript sleep/wait上搜索了很多网页。。。如果你想让JavaScript“RUN,DELAY,RUN”。。。大多数人得到的要么是“RUN,RUN(无用的东西),RUN”,要么是“RUN,RUN+延迟RUN”。。。

我想:这是一个有效的解决方案。。。但你必须把你的跑步代码切碎…:是的,我知道,这只是一个更容易理解的重构。。。还

示例1:

<html>
<body>
<div id="id1">DISPLAY</div>

<script>
// JavaScript sleep by "therealdealsince1982"; copyrighted 2009
// setInterval
var i = 0;

function run() {
    // Pieces of codes to run
    if (i == 0){document.getElementById("id1").innerHTML= "<p>code segment " + i + " is ran</p>"; }
    if (i == 1){document.getElementById("id1").innerHTML= "<p>code segment " + i + " is ran</p>"; }
    if (i == 2){document.getElementById("id1").innerHTML= "<p>code segment " + i + " is ran</p>"; }
    if (i >2){document.getElementById("id1").innerHTML= "<p>code segment " + i + " is ran</p>"; }
    if (i == 5){document.getElementById("id1").innerHTML= "<p>all code segment finished running</p>"; clearInterval(t); } // End interval, stops run
    i++; // Segment of code finished running, next...
}

run();
t = setInterval("run()", 1000);

</script>
</body>
</html>

示例2:

<html>
<body>
<div id="id1">DISPLAY</div>

<script>
// JavaScript sleep by "therealdealsince1982"; copyrighted 2009
// setTimeout
var i = 0;

function run() {
    // Pieces of codes to run, can use switch statement
    if (i == 0){document.getElementById("id1").innerHTML= "<p>code segment " + i + " ran</p>"; sleep(1000);}
    if (i == 1){document.getElementById("id1").innerHTML= "<p>code segment " + i + " ran</p>"; sleep(2000);}
    if (i == 2){document.getElementById("id1").innerHTML= "<p>code segment " + i + " ran</p>"; sleep(3000);}
    if (i == 3){document.getElementById("id1").innerHTML= "<p>code segment " + i + " ran</p>";} //stops automatically
    i++;
}

function sleep(dur) {t=setTimeout("run()", dur);} // Starts flow control again after 'dur'

run(); // Starts
</script>
</body>
</html>

示例3:

<html>
<body>
<div id="id1">DISPLAY</div>

<script>
// JavaScript sleep by "therealdealsince1982"; copyrighted 2009
// setTimeout
var i = 0;

function flow() {
    run(i);
    i++; // Code segment finished running, increment i; can put elsewhere
    sleep(1000);
    if (i == 5) {clearTimeout(t);} // Stops flow, must be after sleep()
}

function run(segment) {
    // Pieces of codes to run, can use switch statement
    if (segment == 0){document.getElementById("id1").innerHTML= "<p>code segment " + segment + " is ran</p>"; }
    if (segment == 1){document.getElementById("id1").innerHTML= "<p>code segment " + segment + " is ran</p>"; }
    if (segment == 2){document.getElementById("id1").innerHTML= "<p>code segment " + segment + " is ran</p>"; }
    if (segment >2){document.getElementById("id1").innerHTML= "<p>code segment "+ segment +" is ran</p>"; }
}

function sleep(dur) {t=setTimeout("flow()", dur);} // Starts flow control again after 'dur'

flow(); // Starts flow
</script>
</body>
</html>

示例4:

<html>
<body>
<div id="id1">DISPLAY</div>

<script>
// JavaScript sleep by "therealdealsince1982"; copyrighted 2009
// setTimeout, switch
var i = 0;

function flow() {
    switch(i)
    {
        case 0:
            run(i);
            sleep(1000);
            break;
        case 1:
            run(i);
            sleep(2000);
            break;
        case 5:
            run(i);
            clearTimeout(t); // Stops flow
            break;
        default:
            run(i);
            sleep(3000);
            break;
    }
}

function run(segment) {
    // Pieces of codes to run, can use switch statement
    if (segment == 0){document.getElementById("id1").innerHTML= "<p>code segment " + segment + " is ran</p>"; }
    if (segment == 1){document.getElementById("id1").innerHTML= "<p>code segment " + segment + " is ran</p>"; }
    if (segment == 2){document.getElementById("id1").innerHTML= "<p>code segment " + segment + " is ran</p>"; }
    if (segment >2){document.getElementById("id1").innerHTML= "<p>code segment " + segment + " is ran</p>"; }
    i++; // Current segment of code finished running, next...
}

function sleep(dur) {t=setTimeout("flow()", dur);} // Starts flow control again after 'dur'

flow(); // Starts flow control for first time...
</script>
</body>
</html>

如果必须处理同步执行,我可以理解睡眠函数的用途。setInterval和setTimeout函数创建一个并行执行线程,该线程将执行序列返回到主程序,如果您必须等待给定的结果,这是无效的。当然,可以使用事件和处理程序,但在某些情况下,这不是预期的。

可以使用带有递增较大值的闭包调用setTimeout()。

var items = ['item1', 'item2', 'item3'];

function functionToExecute(item) {
  console.log('function executed for item: ' + item);
}

$.each(items, function (index, item) {
  var timeoutValue = index * 2000;
  setTimeout(function() {
    console.log('waited ' + timeoutValue + ' milliseconds');
    functionToExecute(item);
  }, timeoutValue);
});

结果:

waited 0 milliseconds
function executed for item: item1
waited 2000 milliseconds
function executed for item: item2
waited 4000 milliseconds
function executed for item: item3

这里的大多数答案都是错误的,或者至少是过时的。没有理由JavaScript必须是单线程的,事实上也不是。今天,所有主流浏览器都支持工人。在此之前,Rhino和Node.js等其他JavaScript运行时支持多线程。

“JavaScript是单线程的”不是有效答案。例如,在工作线程中运行睡眠函数不会阻止UI线程中运行的任何代码。

在支持生成器和yield的较新运行时中,可以在单线程环境中为sleep函数带来类似的功能:

// This is based on the latest ES6 drafts.
// JavaScript 1.7+ (SpiderMonkey/Firefox 2+) syntax is slightly different

// Run code you want to sleep here (omit star if using JavaScript 1.7)
function* main(){
    for (var i = 0; i < 10; i++) {
        // To sleep for 10 milliseconds 10 times in a row
        yield 10;
    }

    yield 5;
    console.log('I just slept 5 milliseconds!');
}

// Resume the given generator after ms milliseconds
function resume(ms, generator){
    setTimeout(function(){
        // Omit .value if using JavaScript 1.7
        var nextSleep = generator.next().value;
        resume(nextSleep, generator);
    }, ms);
}

// Initialize a generator and get first sleep for the recursive function
var
    generator = main(),
    firstSleep = generator.next().value;

// Initialize recursive resume function
resume(firstSleep, generator);

这种对睡眠的模仿不同于真正的睡眠函数,因为它不会阻塞线程。它只是JavaScript当前setTimeout函数之上的糖。这种功能类型已经在Task.js中实现,现在应该可以在Firefox中使用。

另一种可能的方式是:

var _timer;
clearTimeout(_timer);
_timer = setTimeout(function() {
    // Your code
}, 1000); // Delay for 1 s.