Question

167

How to add a callback to a function in javascript

rated 0 times [ 170] [ 3] / answers: 1 / hits: 58108 / 13 Years ago, fri, october 7, 2011, 12:00:00

I have two javascript functions

function one () {

   do something long... like writing jpgfile on disk

}



function two () {

   do something fast... like show the file

}

I call it (in jQuery) like this

 one ();

 two ();

Because function two needs the link file from function one, i need to be sure the execution is completed... so getting the function two in the callback of function one should be the trick.. but how to do that ?

note : I did put an alert ('aaa') between those two functions to let function one complete, and it worked fine... when the alert is commented (removed) nothing works anymore !

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tai

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4 Years ago

answered 13 Years ago tylerdamiena · Accepted Answer

You only need to use a callback if you are doing something asynchronous, otherwise it doesn't matter how long something takes, the next function won't run until the first has finished.

A callback is just passing a function as an argument, and then calling it when done.

function one (callback) {

   do something long... like writing jpgfile on disk

   callback();

}



function two () {

   do something fast... like show the file

}



one(two);

Obviously, if you are doing something asynchronous, then you need something that will tell you when it is finished (such as an event firing).