Javascript: Can't stop the setTimeout

问题

I'm working on a proxy server checker and have the following code to start the requests at intervals of roughly 5 seconds using the setTimeout function;

        function check() {

            var url = document.getElementById('url').value;
            var proxys = document.getElementById('proxys').value.replace(/\n/g,',');

            var proxys = proxys.split(",");

            for (proxy in proxys) {

                var proxytimeout = proxy*5000;

                t = setTimeout(doRequest, proxytimeout, url, proxys[proxy]);

            }
        }

However I can't stop them once their started!

        function stopcheck() {

            clearTimeout(t);

        }

A fix or better method will be more that appreciated.

Thank you Stack Overflow Community!

回答1:

There are 2 major problems with your code:

t is overwritten for each timeout, losing the reference to the previous timeout each iteration.
t is may not be a global variable, thus stopcheck() might not be able to "see" t.

Updated functions:

function check() {
    var url         = document.getElementById('url').value;
    var proxys      = document.getElementById('proxys').value.replace(/\n/g,',');
    var timeouts    = [];
    var index;
    var proxytimeout;

    proxys = proxys.split(",");
    for (index = 0; index < proxys.length; ++index) {
        proxytimeout                = index * 5000;
        timeouts[timeouts.length]   = setTimeout(
            doRequest, proxytimeout, url, proxys[index];
        );
    }

    return timeouts;
}

function stopcheck(timeouts) {
    for (var i = 0; i < timeouts.length; i++) {        
        clearTimeout(timeouts[i]);
    }
}

Example of use:

var timeouts = check();

// do some other stuff...

stopcheck(timeouts);

回答2:

Where is 't' being defined? It keeps being redefined in the for loop, so you will loose track of each timeout handle...

You could keep an array of handles:

var aTimeoutHandles = new Array();
var iCount = 0;
for (proxy in proxys) {

    var proxytimeout = proxy*5000;

    aTimeoutHandles[iCount++] = setTimeout(doRequest, proxytimeout, url, proxys[proxy]);

}

回答3:

Define t outside of both functions first. Additionally, you're overwriting t with each iteration your for loop. Perhaps building a collection of references, and then to stop them you cycle through and clearTimeout on each.

回答4:

You overwrite t each time you set the interval. Thus you only end up clearing the last one set.

回答5:

Looks like you're setting multiple timeouts (one for each proxy), but trying to save them in the same variable. You probably need to use an array there, instead of a simple variable.

回答6:

You have a few problems there:

The main one is that you're overwriting t on each iteration of your for loop; you need an array of ts for your structure to work.
You're using for..in to loop through the indexes of the array. That's not what for..in is for (although there are a lot of people confused about that; see this article). for..in loops through the property names of an object, not the indexes of an array, and therefore this usage breaks in non-trivial situations. Just use an old-fashioned for loop.
You're declaring proxys twice. This is actually harmless, but...
You're not declaring proxy at all (which isn't harmless; it becomes an implicit global).

I've updated the code in Jordan's excellent answer to address those.

来源：https://stackoverflow.com/questions/2060601/javascript-cant-stop-the-settimeout

标签

javascript

for-loop

settimeout