Javascript sleep/delay/wait function

问题:

Sorry if this question has already been asked here before, I could not find a suitable answer.

I am wanting to create a JavaScript sleep/delay/wait function that I can call anywhere in the script, like jQuery's .delay()

I am not able to use setTimeout, as I have a script that is generated by php, and so am not able to put it into two different functions, with the timeout in the middle. I need to create a function that allows me to do

alert("time started");
sleep(4000);
alert("time up");

I really do not want to use jQuery.

回答1:

You cannot just put in a function to pause Javascript unfortunately.

You have to use setTimeout()

Example:

function startTimer () {
    timer.start();
    setTimeout(stopTimer,5000);
}

function stopTimer () {
    timer.stop();
}

EDIT:

For your user generated countdown, it is just as simple.

HTML:

<input type="number" id="delay" min="1" max="5">

JS:

var delayInSeconds = parseInt(delay.value);
var delayInMilliseconds = delayInSeconds*1000;

function startTimer () {
    timer.start();
    setTimeout(stopTimer,delayInMilliseconds);
}

function stopTimer () {
    timer.stop;
}

Now you simply need to add a trigger for startTimer(), such as onchange.

回答2:

You will have to use a setTimeout so I see your issue as

I have a script that is generated by PHP, and so am not able to put it into two different functions

What prevents you from generating two functions in your script?

function fizz() {
    var a;
    a = 'buzz';
    // sleep x desired
    a = 'complete';
}

Could be rewritten as

function foo() {
    var a; // variable raised so shared across functions below
    function bar() { // consider this to be start of fizz
        a = 'buzz';
        setTimeout(baz, x); // start wait
    } // code split here for timeout break
    function baz() { // after wait
        a = 'complete';
    } // end of fizz
    bar(); // start it
}

You'll notice that a inside baz starts as buzz when it is invoked and at the end of invocation, a inside foo will be "complete".

Basically, wrap everything in a function, move all variables up into that wrapping function such that the contained functions inherit them. Then, every time you encounter wait NUMBER seconds you echo a setTimeout, end the function and start a new function to pick up where you left off.

回答3:

The behavior exact to the one specified by you is impossible in JS as implemented in current browsers. Sorry.

Well, you could in theory make a function with a loop where loop's end condition would be based on time, but this would hog your CPU, make browser unresponsive and would be extremely poor design. I refuse to even write an example for this ;)

---

Update: My answer got -1'd (unfairly), but I guess I could mention that in ES6 (which is not implemented in browsers yet, nor is it enabled in Node.js by default), it will be possible to write a asynchronous code in a synchronous fashion. You would need promises and generators for that.

You can use it today, for instance in Node.js with harmony flags, using Q.spawn(), see this blog post for example (last example there).

回答4:

You can use this -

function sleep(milliseconds) {
    var start = new Date().getTime();
    for (var i = 0; i < 1e7; i++) {
        if ((new Date().getTime() - start) > milliseconds){
            break;
        }
    }
}

回答5:

Here's a solution using the new async/await syntax.

async function testWait() {
    alert('going to wait for 5 second');
    await wait(5000);
    alert('finally wait is over');
}

function wait(time) {
    return new Promise(resolve => {
        setTimeout(() => {
            resolve();
        }, time);
    });
}

Note: You can call function wait only in async functions

回答6:

You could use the following code, it does a recursive call into the function in order to properly wait for the desired time.

function exportar(page,miliseconds,totalpages)
{
    if (page <= totalpages)
    {
        nextpage = page + 1;
        console.log('fnExcelReport('+ page +'); nextpage = '+ nextpage + '; miliseconds = '+ miliseconds + '; totalpages = '+ totalpages );
        fnExcelReport(page);
        setTimeout(function(){
            exportar(nextpage,miliseconds,totalpages);
        },miliseconds);
    };
}