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<p class="mb0 mt6">Closed <span title="2014-03-05 11:19:19Z" class="relativetime">6 years ago</span>.</p>
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I would like to know what if i get all my scripts(not vendor) via AJAX request and what's good or bad about it. Would browser cache the response or server would send my script with every request as if user never been to my site?
Performance-wise would that be better, than storing all scripts in footer.
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Getting scripts via AJAX is a bit of confusion in terms, you can use JavaScript to create additional script elements to load extra scripts into the page - which can also be done so asynchronously so it will not block the rendering or download of the page. Take a look for example at the following:
var script = document.createElement('script');
script.src = 'myscript.js';
document.head.appendChild(script);
It creates a new script element, assigns a source and the appends it to the head section of the document. If this was added to the end of the document then the script would be downloaded without having blocked the page loading.
This simple idea is the basis for all (that I know of) front-end JS dependency management - the idea that the requested page only download the assets it needs. You might have heard of JS module definitions such as AMD and CommonJS and that's a huge topic, so I'd recommend taking a read of Addy Osmani's "Writing Modular JavaScript With AMD, CommonJS & ES Harmony" article.
In answer to whether or not they will be cached the answer is yes--in general--though caching depends on many factors both on the server and the user's browser. The individual requests will still need to be made on each subsequent page load which can be slower than one big individual file on a flaky connection. The decision really is down to how users may be accessing your site and whether or not a slight speed decrease initially is worth it vs. developer authoring and maintenance. You can always go for the latter than later on move to the former.
In essence, <script> is by default pulling data into your page synchronously. That might be an issue when scripts are placed in the head section since it might be a blocker for showing your body's content.
Pulling in javascript asynchronously by ajax might usually come handy in case specific minor conditions are met, i.e. most of the users won't use your script in the first place. Let's say you're having a page and should you be logged in as an admin, some additional script is pulled in to handle your admin UI. Or such.
But generally speaking, there's no real advantage in ajaxing javascripts and should you want to avoid broken dependencies (your script being pulled in earlier than your jQuery library, for instance), just stick with your already optimal solution: placing your javascripts as the last thing beforing closing the body tag.
Note also there's new async attribute in the HTML5 draft where it's possible to get script asynchronously ((and therefore speed up loading in theory) even without using AJAX magic. As always though, it's only supported by modern browsers, kicking IE9 and older out of the game.
Hope it helps!