How to speed up the count down?

问题:

I am working on a basic countdown using Javascript where, the countdown starts from 0 and then ends till 24 as thats the idea of the countdown, I want to end it at 24. Here's the code:

var count=0;

var counter=setInterval(timer, 50); //1000 will  run it every 1 second

function timer()
{
  count=count+1;
  if (count >= 24)
  {
     clearInterval(counter);
     //counter ended, do something here
      document.getElementById("countdown").innerHTML=24 ;

     return;
  }

  //Do code for showing the number of seconds here
     document.getElementById("countdown").innerHTML=count ; // watch for      spelling

}

Now the thing is that if you notice this, the countdown happens very fast, this is the intended effect. However the question is this, Is there a way to have a smooth easing type effect, where the countdown starts slowly and then speeds up by the end ? How to achieve that effect ?

Thanks for your response.

EDIT: Here is the fiddle, to see the countdown in action and to gain a deeper insight.

回答1:

Use a timeout which runs only once then add extra time and run the timeout again until you reach 24.

var count=0;
var ms = 200;
var step = 5;
var counter=setTimeout(timer, ms); //1000 will  run it every 1 second

function timer()
{
  count=count+1;
  if (count <= 24)
  {
    //Do code for showing the number of seconds here
     document.getElementById("countdown").innerHTML=count ; // watch for spelling
     ms = ms - step;
     counter = setTimeout(timer, ms);

  }

}

回答2:

You'll need to use setTimeout instead of setInterval and another variable for setTimeout.

    var count=0;
    var speed = 1000;
    timer();

    function timer()
    {
      count++;

      //Do code for showing the number of seconds here
         document.getElementById("countdown").innerHTML=count ; // watch for      spelling

      if (count >= 24)
      {
         return;
      }

      speed = speed / 6 * 5; // or whatever
      setTimeout(timer, speed);

    }

Fiddle: http://jsfiddle.net/4nnms1gz/2/

回答3:

Using setTimeout will give you more control on your counter.Here is a working example where you can handle the speed of your counter.It will give you a time increase of 30ms to 70ms to each call to time function

var count=0;
var loop=1000;
var interval;

var text=document.getElementById('countdown');
var range=document.getElementById('range');
var btn=document.getElementById('btn');
var span=document.getElementById('val');

range.addEventListener('change',function(e){
   span.innerHTML=range.value+' ms';
});
btn.addEventListener('click',function(e){
   timer(parseInt(range.value));
 
});

function timer(time)
{
  
   console.log(time);
  if (count < 24)
  {
     count=count+1;
     text.value=count;
	 
	  
     loop-=time;
	 
	 interval=setTimeout(function(){
                            timer(time);
                         },loop);
	 
     if(count>=24){
	   clearTimeout(interval);
	   return;
	 }
  }
  

}

<input type='text' id='countdown' value='0'></br>
<input type='range' id='range' max='70' min='30' value='30' >increase by:<span id='val'></span></br>

<input type='button' value='start' id='btn' ></br>