settimeout - Is there a correct way to 'yield' in the cooperative threading sense in javascript? - Stack Overflo

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I'm writing a ubiquity plugin the long function callback for an ajax query is blocking up the GUI Thread causing firefox to lock up.

The obvious solution seem to be to use some sort of deferred execution of (i.e we want to periodically add the carry out doing this query function to the end of the event queue and then allow other mands to be carried out.

The only way I can think of doing this is to use settimeout with a timeout of zero... is this is guaranteed to work, or is there a better way of doing this.

I'm writing a ubiquity plugin the long function callback for an ajax query is blocking up the GUI Thread causing firefox to lock up.

The obvious solution seem to be to use some sort of deferred execution of (i.e we want to periodically add the carry out doing this query function to the end of the event queue and then allow other mands to be carried out.

The only way I can think of doing this is to use settimeout with a timeout of zero... is this is guaranteed to work, or is there a better way of doing this.

• javascript
• settimeout
• ubiquity
• reactor

Share Improve this question Follow asked Sep 20, 2009 at 21:31 user47741user47741 3,01544 gold badges2323 silver badges1414 bronze badges 1

• How are you doing the AJAX? If you're loading a script tag, that could be blocking (browser blocks until the script es back). – Steve Brewer Commented Sep 21, 2009 at 4:16

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2 Answers 2

Sorted by: Reset to default 8

Using setTimeout with a very small timeout (0 or very nearly zero if you're feeling paranoid) is the only way to do this in a browser context. It works very well and is very reliable, but be sure to yield often enough but not too often, as it does take a while to e back to you ("a while" in a puter sense, of course; it's almost instantaneous [modulo other things you may be doing] in human terms).

Make sure you are using an asynchronous request as a synchronous request blocks the browser (which would explain the GUI lock-up).

If this is not your problem, I think you want something like this task queue.

var queue = [];

queue.push(someTaskFunction);
queue.push(anotherTaskFunction);
// ...

var runQueue = (function () {
    var len = queue.length, task = 0;
    for (; task < len; task++) {
        yield queue[task]();
    }
}());

Call runQueue.next() to execute the next task. Wrap it in a try..catch statement as such:

try {
    runQueue.next();
} catch (e if (e instanceof StopIteration)) {}

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