How to apply Content editor on whole site in SP 2013

Question

I have a js script and I want to apply it on a whole SP site. I inserted a content editor webpart on the start page and it works fine, but now i want to apply it on the whole site. Do I have to go through every page and insert a content editor webpart with the lines I need, or is there way to put it on one place and apply it on the whole site?

script.js:

$(function () {
getUser();
});

function getUser() {
    var clientContext = new SP.ClientContext();
    var web = clientContext.get_web();
    var user = web.get_currentUser();
    clientContext.load(user);
    clientContext.executeQueryAsync(function(){
        var leftNav = document.getElementById("DeltaTopNavigation");
        leftNav.innerHTML += "<p>User:" + user.get_title() + "</p>";
        //document.write("<p>User:" + user.get_title() + "</p>");
    }, function(){alert(":(");});

}

and i calling it with this code in the content editor/seattle.master:

<script type="text/javascript" src="/_layouts/15/sp.runtime.js"></script>
<script type="text/javascript" src="/_layouts/15/sp.js"></script>
<script type="text/javascript" src="/{PATH}/jquery-latest.min[1].js"></script>
<script type="text/javascript" src="/{PATH}/script.js"></script>

Answer 1

If you want to apply script to whole site, than you have to modify your Masterpage. You cant apply scripts to whole site using content editor unless you manually place content editor webparts on each and every page in the site.

To achieve what you want, just follow this simple steps

Just go to sharePoint designer-->make a copy of default Masterpage--> set custom Masterpage as default Masterpage-->place your script in Masterpage!