Execute javascript callback from within "script" tag after loading a javascript file

Question

I want to execute a javscript callback from within the <script> tag after loading a javascript file, using query string callback=MyCallbackFuntion.

Something similar to

<script src="http://gdata.youtube.com/feeds/users/USER/uploads?
        alt=json-in-script
        &max-results=30
        &callback=listVideosCallback" 
    type="text/javascript"></script>

Here at the end of src=http://..., youtube uses the query string ?callback= listVideosCallback to execute the function listVideosCallback() after the data/file is loaded. How can I do something similar?

Community · Accepted Answer · 2017-05-23 12:05:14Z

1

Your server script should do something like (this example is PHP):

echo $_GET['callback'] . '(' . json_encode($data) . ');';

What is JSONP all about?

When you use <script src="URL"></script>, the browser downloads the URL, and then executes the Javascript code that it contains. If that code looks like:

MyCallbackFunction(data);

then loading the script will cause the function to be called with the data as a parameter. So the server script should get the function name from the callback URL parameter, and turn it into a function call by putting parentheses and a literal data object after it and echoing this.

edited May 23, 2017 at 12:05

CommunityBot

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answered Sep 19, 2013 at 17:11

Barmar

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5 Comments

Reinstate Monica Cellio Over a year ago

Don't forget the empty parenthesis ;)

Muhammad Reda Over a year ago

Where exactly should this line go ?!

Barmar Over a year ago

In the server script that you're running with the <script> tag.

Barmar Over a year ago

I've added some more explanation, I hope it helps.

Katelynn ruan Over a year ago

make no sense to me

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