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plurals

PO
primarykey
Id
7070714
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
1
CommunityOwnedDate
CreationDate
2011-08-15T20:51:57.560
FavoriteCount
0
LastActivityDate
2012-12-10T20:09:56.773
LastEditDate
2012-12-10T20:09:56.773
LastEditorUserId
1159255
OwnerUserId
698791
ParentId
7070495
PostTypeId
2
Score
18
ViewCount
0
LastEditorDisplayName
text
Body
The main browser process is a single threaded event loop. If you execute a long-running operation within a single-threaded event loop, the process "blocks". This is bad because the process stops processing other events while waiting for your operation to complete. 'alert' is one of the few blocking browser methods: if you call alert('test'), you can no longer click links, perform ajax queries, or interact with the browser UI. In order to prevent blocking on long-running operations, the XMLHttpRequest provides an asynchronous interface. You pass it a callback to run after the operation is complete, and while it is processing it cedes control back to the main event loop instead of blocking. There's no reason to use a callback unless you want to bind something to an event handler, or your operation is potentially blocking and therefore requires an asynchronous programming interface. <a href="http://www.yuiblog.com/blog/2010/08/30/yui-theater-douglas-crockford-crockford-on-javascript-scene-6-loopage-52-min/" rel="noreferrer">This is an excellent video discussing more about the event loop used in the browser, as well as on the server side in node.js.</a> EDIT: that convoluted line from the jQuery documentation just means that the callback executes asynchronously as control is ceded back to the main event loop. <pre><code>parent_function(function () { console.log('Callback'); }); parent_doesnt_block(); // <-- function appears after "parent" therefore_execution_continues(); // Maybe we get 'Callback' in the console here? or maybe later... execution_still_continues(); </code></pre>
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1. POWhy use callback in JavaScript, what are its advantages?
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1. USbergren2
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1. USEMI
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1. POWhy use callback in JavaScript, what are its advantages?
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