Show HN: Cross-browser asynchronous JS script loader w/callbacks

https://github.com/niftylettuce/javascript-async-callback

by niftylettuce • 14 years ago

45 23 14 years ago

github.com

alagappanr• 14 years ago

The question might be naive, but can you tell me the advantage of using this?

pizza• 14 years ago

Basically, it lets you run a function once a javascript file has been loaded.

jonny_eh2• 14 years ago

Normally, you would load javascript files by inserting a <script src="whatever.js"> tag into your HTML document's <HEAD> or <BODY>. The big disadvantage to that is it's synchronous. That means no rendering or executing of javascript can occur while that js file is being run.

This library would allow you to run it asynchronously, so that other js code can continue to run.

spicyj• 14 years ago

Would be nice if conditional comments weren't used so that it's compatible with most JS minifiers.

jonthepirate• 14 years ago

Similar to require.js but I like it!

ashray• 14 years ago

Nice work! Definitely simplifies stuff. Are you thinking of integrating writecapture [1] for a document.write override option ? Might be a nifty thing to do since a lot of external scripts use that and can block access or worse, clear the DOM on an async load.

[1] http://github.com/iamnoah/writeCapture

taf2• 14 years ago

thank you for posting code!

the problem with this solution is you had to include a blocking js script first to use it... a better solution is to inject your script and for callbacks use an array. Look at how GA.js works, this is all it does, push functions onto an Array (builtin) and once the code loads start pop'ing functions to invoke off the array see: https://gist.github.com/3616965

to make it even better replace the push method on the Array with the invoke method meaning once the code's are loaded - you have immediate invoke of functions... someone should spell this out clearer but it makes me sad to not see this technique used more... it's tiny. see: https://gist.github.com/3616991

updated with two version and formated.

muyuu• 14 years ago

Good stuff. I guess this is quite compatible as well.

jonny_eh2• 14 years ago

Cool stuff, very handy. Next step, add dependancy support. Maybe pass in an array of scripts, along with their dependancies, and load them all in the right order.

OmarIsmail• 14 years ago

I'm seeing some pretty fundamental issues here. I suppose if you assume that you'll have total control of everything loaded then some of the assumptions made here may be an ok trade off, but from my experience it's better practice to be more guarded.

Specifically:

1) the window.onload is being directly overwritten without any chaining. The safe way is to first store a reference to whatever was in .onload beforehand and call that in the overwritten onload.

2) the load check uses an interval on a 10ms timer. Chained setTimeouts are much better for performance and 10ms is quite an aggressive default. 50ms gets called 5x fewer and has a imperceptible difference to the user.

3) _async is some big ol' global var with no function scoping at all.

phoboslab• 14 years ago

How has setTimeout "much better performance" than setInterval? It's a myth that setInterval queues up function calls if they take a long time, if that's what you're referring to.

anatoli• 14 years ago

"Much better performance" is perhaps a bit misleading since it's not black and white, but at the core OP is right. See this thorough SO answer for more info: http://stackoverflow.com/a/731625/886402

scriby• 14 years ago

Not sure why I would use this when other solutions like LABjs are rock solid, fully featured, and small (~2k zipped).

http://labjs.com/

przemoc• 14 years ago

It's good to know other, already used, mature solutions.

yepnope is an asynchronous conditional resource loader that's super-fast, and allows you to load only the scripts that your users need. 1.7kb minified and gzipped. Check it out!

http://yepnopejs.com/

https://github.com/SlexAxton/yepnope.js

Another Script Loader?#?@$!@# - Why Use Yepnope? - quoting conclusion from the page:

> In short, we want you to make the right decision for your application. We can certainly think of times when yepnope.js would not be the correct choice for a resource loader, and we hope we've made those situations abundantly clear in our documentation. However, we also think that yepnope meets a lot of people where they are, when it comes to a balance of performance, usability, size and feature-set.

> If you have questions about if yepnope is right for your application. Send us a tweet or an email and we'll help you out. Most of us in the script-loader author scene are total BFFs and we aren't about competition, we're about pushing the edge. In other words, we totally use LABjs and RequireJS in a bunch of our projects, because they're badass (and the other ones are probably great too!).

huskyr• 14 years ago

I wrote something similar some time ago:

https://github.com/hay/jsdynaload

Allows you to do something like this:

jsDynaLoad(['1.js', '2.js', '3.js'], function() { console.log('callback'); });

culshaw• 14 years ago

Nice work, I would change that you are browsers sniffing to detecting variables declared in the window for webkit prefixes.

wamatt2• 14 years ago

Nifty, thanks for sharing. :)

Also, as others have mentioned, there are plenty of options out there, so it might be useful highlight any specific difference or advantage this solution provides over LabJS, RequireJS, Yepnope, curl.js etc

On a side note, there is a rather comprehensive feature matrix of a number of popular JS loaders https://spreadsheets.google.com/lv?key=tDdcrv9wNQRCNCRCflWxh...

niftylettuce4• 14 years ago

EDIT: put the repo back up to not cause broken link here... and added a notice to keep people from starring it

i (originally) took the repo down b/c so many people starred it and i didnt want them to be scarred :) never saw that spreadsheet b4, thx for posting. a lot of good discussion in this thread. the project was just a little hack rewrite, i never stated anywhere it was better than anything else and you guys can see why :) feedback is great. i did run some tests on it and it is surprisingly almost as fast/faster +/- as similar solutions though! haha.

wamatt2• 14 years ago

Given that you probably didn't know about many existing solutions, it's rather great you wrote your own, after realizing a need :)

I'd keep the repo up! (even if the feedback is a bit daunting)

teh_klev• 14 years ago

Nothing to see now. Yanked by OP:

https://twitter.com/niftylettuce/status/242946633367683075

niftylettuce4• 14 years ago

see http://news.ycombinator.com/item?id=4474094

niftylettuce4• 14 years ago

See https://gist.github.com/3620903#comments for a better solution!

Show HN: Cross-browser asynchronous JS script loader w/callbacks

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