Intervals and Timeouts

 Intervals

 1 var num = 0;
 2 var max = 10;
 3 
 4 function incrementNumber(){
 5   num++;
 6   
 7   // if the max has not been reached, set another timeout
 8   if(num < max){
 9     setTimeout(incrementNumber, 500);
10   } else {
11     alert("Done");
12   }
13 }
14 
15 setTimeout(incrementNumber, 500)

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Timeouts

 1 var num = 0;
 2 var max = 10;
 3 
 4 function incrementNumber(){
 5   num++;
 6   
 7   // if the max has not been reached, set another timeout
 8   if(num < max){
 9     setTimeout(incrementNumber, 500);
10   } else {
11     alert("Done");
12   }
13 }
14 
15 setTimeout(incrementNumber, 500)

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 　　Note that when you‘re using timeouts, it is unnecessary to track the timeoutID, because the execution will stop on its own and continue only if another timeout is set. The pattern is considered a best practice for setting intervals without actually using intervals. True intervals are rarely used in production environments because the time between the end of one interval and the beginning of the next is not necessarily guaranteed, and some intervals may be skipped. Using timeouts, as in the preceding example, ensures that can‘t happen. Generally speaking, it‘s best to avoid intervals. 

Intervals and Timeouts

原文：http://www.cnblogs.com/linxd/p/4515676.html