在一段时间后重复执行功能的良好模式是什么？

Question

Using setInterval/ setTimeout, how can I make sure my function FINISH executing before waiting for some time and then executing again, FINISH, then wait, and so on. Thanks.

Answer 1

That's the classic use case for a chained series of setTimeout :

setTimeout(foo, yourInterval);
function foo() {
    // ...do the work...

    // Schedule the next call
    setTimeout(foo, yourInterval);
}

Since setTimeout only schedules a single call to the function, you reschedule it (if appropriate) after the function has done its work.

Unlike setInterval , this works correctly even if the work your function does is asynchronous, as long as you reschedule it from the callback of the asynchronous work. For example:

setTimeout(foo, yourInterval);
function foo() {
    callSomethingAsynchronous(function() {
        // ...we're in the async callback, do the work...

        // ...and now schedule the next call
        setTimeout(foo, yourInterval);
    });
}

In contrast, if you're doing something asynchronous, using setInterval rapidly becomes chaotic.

Answer 2

function execute_and_wait( repeated_function, time_delay ) {
    var next_run = function () {
        var complete_callback = function () {
            next_run();
        }
        var killcode = setTimeout(
            function () {
                repeated_function(complete_callback);
            },
            time_delay 
        );
        return killcode;
     };
     return next_run;
}

Usage :

// Runs a function that prints hi every 2 seconds
// Kills it after 10 seconds
var ka = function (r) { alert('hi'); r(); };
var runka = execute_and_wait(ka,2000);
var killka = runka();
setTimeout( 
   function () {
       clearTimeout(killka);
   },
   10000
);