我可以在另一个 setTimeout 的处理程序中有一个 setTimeout 吗？

Question

Here's a quick (broke) jsfiddle: http://jsfiddle.net/wH2qF/

This isn't working for some reason... is it because I have a setTimeout inside a handler of another setTimeout?

$(function() {
   $("#Volume").click(function() {
      setTimeout(triggerVolumeChange, 4000);
      function triggerVolumeChange() 
      {
          var volumeDiv = document.getElementById("volumeNumber");
          var volumeOld = 8;
          var volumeNew = 37;
          var timeNew = (1000/(volumeNew-volumeOld));
          changeVolume();
                        
          function changeVolume()
          {
             volumeDiv.innerHTML = volumeOld;
             volumeOld++;
             if (volumeOld <= volumeNew) setTimeout(changeVolume, timeNew);
          };
      });
});

Should specify that for clarity purposes I deleted other things from that Click function, and also to clarify what doesn't work exactly, well, basically, I click and nothing happens, whereas if I cut out this chunk of code it works fine... actually the setting of the vars also work fine (naturally I presume) but when I paste or uncomment the changeVolume() function then the click stops working again... Any thoughts?

--

Another piece of clarification: What I'm trying to do is, on click, simulate the volume going from value 8 to 37, in a string.. thus the setTimeout inside that function.

--

As per your guy's request, here's the entire code... I doubt it will make sense, but here it is... FYI, on click this will trigger a number of animations to simulate the flow of an application I'm designing..

<script>
            $(function() {
                $("#Volume").click(function() {
                                        
                    var userPrompt = document.getElementById("userPrompt")
                    userPrompt.innerHTML = "Change volume to 37";
                                        
                    var avatarIcon = document.getElementById("avatarIcon");
                    avatarIcon.innerHTML = "<img src='imgs/haloIcons-volume_82x76.png' alt='Volume'/>";
                
                    var hints = document.getElementById("hints");
                    hints.style.opacity = 0;
                    $(".dragonTvOut").toggleClass("dragonTvIn");
                    
                    setTimeout(triggerP, 1000);
                    function triggerP()
                    {
                        var halo = document.getElementById('avatar');
                        if( 'process' in halo ) { 
                            halo.process();
                        };
                    };
                    
                    setTimeout(triggerUserPrompt, 2000);
                    function triggerUserPrompt() 
                    {
                        document.getElementById("userPrompt").className = "userPromptIn";
                    };
                    
                    setTimeout(triggerVolumeChange, 4000);
                    function triggerVolumeChange() 
                    {
                        document.getElementById("userPrompt").className = "userPromptEnd";
                        
                        var halo = document.getElementById('avatar');
                        if( 'resume' in halo ) { 
                            halo.resume();
                        }

                        document.getElementById("avatarIcon").className = "avatarIconEnd";
                        
                        var volumeDiv = document.getElementById("volumeNumber");
                        var volumeOld = 8;
                        var volumeNew = 37;
                        var timeNew = (1000/(volumeNew-volumeOld));
                        changeVolume();
                        
                        function changeVolume()
                        {
                            volumeDiv.innerHTML = volumeOld;
                            volumeOld++;
                            if (volumeOld <= volumeNew) setTimeout(changeVolume, timeNew);
                        }​;
                        
                        var side = 100;
                        var paper = new Raphael(volumeArcAnim, 100, 300);
                        
                        paper.customAttributes.arc = function (xloc, yloc, value, total, R) {

                            var alpha = 360 / total * value,
                                a = (90 - alpha) * Math.PI / 180,
                                x = xloc + R * Math.cos(a),
                                y = yloc - R * Math.sin(a),
                                path;
                            if (total == value) {
                                path = [
                                    ["M", xloc, yloc - R],
                                    ["A", R, R, 0, 1, 1, xloc - 0.01, yloc - R]
                                ];
                            } else {
                                path = [
                                    ["M", xloc, yloc - R],
                                    ["A", R, R, 0, +(alpha > 180), 1, x, y]
                                ];
                            }
                            return {
                                path: path
                            };
                        };
                    
                        var arcWidth = 87;
                        var strokeRadius = arcWidth/2;
                        
                        var indicatorArc = paper.path().attr({
                            "stroke": "#ffffff",
                            "stroke-width": 3,
                            arc: [side/2, side/2, 12, 100, strokeRadius]
                        });
                        
                        indicatorArc.animate({
                            arc: [side/2, side/2, 60, 100, strokeRadius]
                        }, 1500, "<>", function(){
                            // anim complete here
                        });
                        
                    };
                                            
                });
            });
            </script>

Answer 1

Yes, you can have a setTimeout() inside another one -- this is the typical mechanism used for repeating timed events.

The reason yours isn't working is not to do with the setTimeout() itself; it's to do with the way you've nested the functions.

The changeVolume() function being inside triggerVolumeChange() means that you can't reference it directly using its name.

The quickest solution for you would be to remove the nesting, so that changeVolume() is at the root level rather than nested inside triggerVolumeChange() .

Answer 2

You're missing an } :

$(function() {
   $("#Volume").click(function() {
      setTimeout(triggerVolumeChange, 4000);
      function triggerVolumeChange()
      {
          var volumeDiv = document.getElementById("volumeNumber");
          var volumeOld = 8;
          var volumeNew = 37;
          var timeNew = (1000/(volumeNew-volumeOld));
          changeVolume();

          function changeVolume()
          {
             volumeDiv.innerHTML = volumeOld;
             volumeOld++;
                 if (volumeOld <= volumeNew) setTimeout(changeVolume, timeNew);
          };
      } // that one was missing
   });
});

Answer 3

In your broken example http://jsfiddle.net/wH2qF/ there are a few problems

• You forgot to tell jsfiddle to use jQuery
• The id of the volume span (in JS) was ph but should be volumeNumber (as in the HTML)

Click here to see a working version

Had you selected jQuery from the libraries in jsfiddle, you would have seen an error

Uncaught TypeError: Cannot set property 'innerHTML' of null

That leads me to believe that your jsfiddle is not a good representation of your problem. Maybe try to create another reduction since the one you added only had "silly" errors?

Answer 4

If you don't want to use setInterval() , you can make the code work with these changes:

$(function() {
    $("#Volume").click(function() {
        setTimeout(triggerVolumeChange, 4000);
        function triggerVolumeChange () {
            var volumeDiv = document.getElementById("volumeNumber");
            var volumeOld = 8;
            var volumeNew = 37;
            var timeNew = (1000/(volumeNew-volumeOld));
            var changeVolume = function () {
                volumeDiv.innerHTML = volumeOld;
                volumeOld++;
                if (volumeOld <= volumeNew) setTimeout(changeVolume, timeNew);
            };
            changeVolume();
        }
    });
});

Working demo at jsFiddle .

Answer 5

Technically there is no difference where the timer is initiated from. In most cases it is implemented as list of the timers with an identifiers and associated callback handlers.

So it will be ok if your logic is correct. There is no unpredictable conditions that bring infinite call sequences, and there is no infinite amount of timeout instances and so on.

For example imitation of setInterval function:

// Bad (unexpected multiple sequences started per each event)

const handler = () => {
  setTimeout(handler)
}

<Button onClick={handler} />

// Good (previous interval closed before start new one)

const [id, idUpdate] = useState(-1)

const handler = () => {
  const id = setTimeout(handler)
  idUpdate(id)
}

const start = () => {
  if(id !===-1) clearTimeout(id)
  idUpdate(-1)
  handler()
}

<Button onClick={start} />

or some else

// Bad (infinite events with small time will take all cpu time)

const handler = () => {
  setTimeout(handler, 0) // actually mean several ms
}

// Good (special condition for finish iterations)

let count = 20

const handler = () => {
  if(!count) return
  count--
  setTimeout(handler, 0)
}