Is it possible to wait until all javascript files are loaded before executing javascript code?

You can use

$(window).on('load', function() {
    // your code here
});

Which will wait until the page is loaded. $(document).ready() waits until the DOM is loaded.

In plain JS:

window.addEventListener('load', function() {
    // your code here
})

You can use .getScript() and run your code after it loads:

 $.getScript("my_lovely_script.js", function(){

    alert("Script loaded and executed.");
    // here you can use anything you defined in the loaded script

 });

You can see a better explanation here: How do I include a JavaScript file in another JavaScript file?

You can use <script>'s defer attribute. It specifies that the script will be executed when the page has finished parsing.

<script defer src="path/to/yourscript.js">

A nice article about this: http://davidwalsh.name/script-defer

Browser support seems pretty good: http://caniuse.com/#search=defer

Another great article about loading JS using defer and async: https://flaviocopes.com/javascript-async-defer/

Expanding a bit on @Eruant's answer,

$(window).on('load', function() {
    // your code here
});

Works very well with both async and defer while loading on scripts.

So you can import all scripts like this:

<script src="/js/script1.js" async defer></script>
<script src="/js/script2.js" async defer></script>
<script src="/js/script3.js" async defer></script>

Just make sure script1 doesn't call functions from script3 before $(window).on('load' ..., make sure to call them inside window load event.

More about async/defer here.