javascript - setTimeout continuous loop without wait - Stack Overflow

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I'm trying to get setTimeout to re-run the function it's inside after 15 seconds, it's not waiting 15 seconds and just doing it in a constant loop.

Here's my current code

function checkSession(x) {
http.abort();
http.open("GET", siteURL+"processes/ajax.php?call=check_session&string="+x+"&new="+Math.random(), true);
http.onreadystatechange = function() {
    if(http.readyState == 4) {
        if(http.responseText == true) {
            updateSession(x);
        } else {
            setTimeout(checkSession(x),15000);
        }
    }
}
http.send(null);
}

I don't see any problems in the code itself, the only thing wrong is that it's just doing a constant loop without waiting the "15000" miliseconds.

I'm trying to get setTimeout to re-run the function it's inside after 15 seconds, it's not waiting 15 seconds and just doing it in a constant loop.

Here's my current code

function checkSession(x) {
http.abort();
http.open("GET", siteURL+"processes/ajax.php?call=check_session&string="+x+"&new="+Math.random(), true);
http.onreadystatechange = function() {
    if(http.readyState == 4) {
        if(http.responseText == true) {
            updateSession(x);
        } else {
            setTimeout(checkSession(x),15000);
        }
    }
}
http.send(null);
}

I don't see any problems in the code itself, the only thing wrong is that it's just doing a constant loop without waiting the "15000" miliseconds.

• javascript
• html
• ajax

Share Improve this question Follow asked Jan 22, 2013 at 16:31 Curtis CreweCurtis Crewe 3399 bronze badges

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2 Answers 2

Sorted by: Reset to default 9

change the setTimeout call to:

setTimeout(function(){checkSession(x)},15000);

As you have it now, checkSession is called immediately and then passed as an argument to setTimeout. Wrapping it inside the function allows for the call to be deferred.

Your explanation:

The function is like this: setTimeout( function, delay );

Your method call was not setting an anonymous function or reference to a function as the function argument.

Wrong: setTimeout(checkSession(x),15000);

Reason: checkSession(x) is a function call, not a reference to a function or anonymous function

Right: setTimeout(function() {checkSession(x) },15000);

Reason: the function call is now wrapped as an anonymous function in place and the function argument is set for the setTimeout( function, delay ) method.

Hope that helps to clear it up for you!

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