The community is working on translating this tutorial into Portuguese, but it seems that no one has started the translation process for this article yet. If you can help us, then please click "More info".
If you are fluent in Portuguese, then please help us - just point to any untranslated element (highlighted with a yellow left border - remember that images should have their titles translated as well!) inside the article and click the translation button to get started. Or have a look at the current translation status for the Portuguese language.
If you see a translation that you think looks wrong, then please consult the original article to make sure and then use the vote button to let us know about it.
Please help us by translating the following metadata for the article/chapter, if they are not already translated.
If you are not satisfied with the translation of a specific metadata item, you may vote it down - when it reaches a certain negative threshold, it will be removed. Please only submit an altered translation of a metadata item if you have good reasons to do so!
Aborting an AJAX request
There may be situations where you need to cancel a running AJAX request before it ends. It's usually in cases where the user might perform an action, which sets of an AJAX request, several times within a short time period. A good example of this is auto-complete functionality for a search box, where you might try to help the user by finding related search terms based on their current input, by making an AJAX request each time they press a key in the search field. In that case, it's very likely that the user types faster than your AJAX request can be performed and therefore you would want to abort any non-finished requests, before starting the next one. Consider the following example:
It requests a PHP script which is doing a very complicated calculation (as you will see from the result), which means that it usually takes ~3 seconds to finish. Now, try the example and push the button several times after each other. The same "calculation" will be performed multiple times and the result will also be displayed multiple times (with a 3 second delay).
Fortunately, a call to the get() method and pretty much any other jQuery AJAX method, returns an object which, among others, contains an abort() method. We can save this reference and then call the abort() method on it if needed. Have a look at this slightly modified example:
We start off by defining a common variable for containing the request reference. In the PerformAbortableCalculation() method, we assign the return value of the get() call to this variable, but before we do so, we check to see if it's null (the method hasn't been used yet) and if not, we call the abort() method on it. If you try this example and click several times, you will see that no matter how many times you click the button, it only executes the callback function once.