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October 10th, 2008, 12:25 pm

joebert,

I admit that sleeping in JavaScript is a kludgy thing to do, especially if we're talking about a Web application. Any time I consider sleeping, I usually come up with a more elegant solution.

I came across this discussion because I finally found a case where I really did want to sleep. I was developing a quick-and-dirty tool to evaluate the skills of software testers. It's a specialized calculator with all sorts of deliberate bugs. When interviewing candidates, I present them with this buggy calculator, give them a few minutes, observe their technique and tabulate how many defects they find. One of the defects is that the user interface becomes slow to respond under certain conditions. I use a sleep function to create this latency.

October 11th, 2008, 11:35 pm

I have one that my AJAX class uses to wait for retry or something like that. This topic has a crazy hits, wow.

October 31st, 2008, 8:17 am

joebert wrote:

I still can't figure out what use a sleep function for JS is.

Okay, here is why I need it: I am programming a multi-player game based on the old "concentration" game where you flip over two cards and if they match, you get a point. Otherwise play moves to the next player.

Now this work's great when you're playing it on a table and you see what cards the other player flipped, but when you're playing online and are at a different computer, I want to reveal the two cards that were flipped to the remote players, and I think it is more pleasing (and realistic) to flip one card over, wait a second, then flip the second one.

Okay, sure, I can certainly work around this with timeouts, etc. But really all I want is a simple sleep function so I can do this:

Code: [ Download ] [ Select ]

revealCard (card1);
sleep (1000);
revealCard (card2);
sleep (1000);
clearCards ();
 
// I would prefer to get control back here after cards are cleared.

1. revealCard (card1);
2. sleep (1000);
3. revealCard (card2);
4. sleep (1000);
5. clearCards ();
6.  
7. // I would prefer to get control back here after cards are cleared.

Instead, my solution is:

Code: [ Download ] [ Select ]

revealCard (card1);
setTimeout("revealCard ("+card2+")", 1000);
setTimeout("clearCards()", 2000);
setTimeout("restOfCode("+var1+","+var2+",...,"+varN+")", 3000);

1. revealCard (card1);
2. setTimeout("revealCard ("+card2+")", 1000);
3. setTimeout("clearCards()", 2000);
4. setTimeout("restOfCode("+var1+","+var2+",...,"+varN+")", 3000);

where restOfCode is the code I want to execute after clearing cards, and var1-varN are the local variables I now want to pass to this code.

We can debate which is more elegant, but I personally think the sleep version is more straightforward.

...Lance

February 24th, 2009, 7:37 am

I think this can be solved with the setTimeout function. At least in the
case where one wants to delay in a loop. If one creates a while-loop
between two functions the timeout can be used in one end.

Code: [ Download ] [ Select ]

 
function do_something(i) {
   if (i > 30)
     return;
   // do soemthing
   setTimeout("loop_implementation("+i+")", 10000);
}
 
function loop_implementation(i) {
   i = i + 1;
   do_something(i);
}
 

1.  
2. function do_something(i) {
3.    if (i > 30)
4.      return;
5.    // do soemthing
6.    setTimeout("loop_implementation("+i+")", 10000);
7. }
8.  
9. function loop_implementation(i) {
10.    i = i + 1;
11.    do_something(i);
12. }
13.  

This way one can call do_something with 0 and it will be done 30
times with a 10 sec. delay between the steps. For an infinite loop
just replace return with setting i = 0.

--
Øyle

February 24th, 2009, 7:38 am

s/30/31/

February 24th, 2009, 7:51 am

General case.

Code: [ Download ] [ Select ]

 
function do_something(i) {
   switch(i) {
     case 0:
       before_wait();
       break;    
     case 1:
       after_wait();
       break;
     default:
       return;
   }
   setTimeout("loop_implementation("+i+")", 10000);
}
 
function loop_implementation(i) {
   i = i + 1;
   do_something(i);
}
 
function before_wait() {/* something */}
function after_wait() {/* something else */}
 

1.  
2. function do_something(i) {
3.    switch(i) {
4.      case 0:
5.        before_wait();
6.        break;    
7.      case 1:
8.        after_wait();
9.        break;
10.      default:
11.        return;
12.    }
13.    setTimeout("loop_implementation("+i+")", 10000);
14. }
15.  
16. function loop_implementation(i) {
17.    i = i + 1;
18.    do_something(i);
19. }
20.  
21. function before_wait() {/* something */}
22. function after_wait() {/* something else */}
23.  

--
Øyle