How to redirect all but a few users to a custom page in SharePoint 2013

Imagine that you are working in a production environment, you're close to your deadline on which all users will be granted access to your site. But what if you're not ready yet? What if your supervisor wants you to "deny" all users access to the site by redirecting them to one page, all users except for a select few?

In such a case, you'll need a script that will check the name of the user, see if he/she is allowed full access to the site, and if not redirect the user to a custom page. I used Jane Doe and John Doe as the users that are allowed full access to the site (I advise you to add your own name as well).

The code

We need to make a JavaScript file (I named mine "custom-redirect.js") and we will add the following code to the file:

SP.SOD.executeFunc('sp.runtime.js');
SP.SOD.executeOrDelayUntilScriptLoaded('SP.UserProfiles.js', 
 "~sitecollection/Style Library/Scripts/jquery.SPServices-2013.01.js");

var url = window.location.pathname;
if (url.indexOf('Redirect.aspx') > -1) {
 // Do not run the script if we're already on the page.
}
else {
 function redirectMe() {
  var userListArray = new Array();
  userListArray.push("Jane Doe"); 
  userListArray.push("John Doe"); 

  var user = $().SPServices.SPGetCurrentUser({ 
   webURL: "", 
   fieldName: "Title", 
   fieldNames: {}, 
   debug: false
  });
 
  function include(arr, obj) {
   for (var i = 0; i < arr.length; i++) {
    if (arr[i] == obj) return true;
   }
  }

  if(include(userListArray,user)) {}
  else { 
   window.location = 
    "http://your-site-here.com/Pages/Redirect.aspx";
  }
 }
}

The code will check if we're not on the redirect page already, since there's no need to keep running the script when the user has already been redirected. If we're not, then we'll continue with the function called redirectMe().

We need to make an array that will hold the names of all users that will be granted full access to the site. Push the names of those users to the array.

Then, we use SPServices to check the "Title" (also known as the full name of the user) of the current user. We will need a small function to check if an array contains an object as well. Using that function, we then check if the name of the current user is included in the array. If it is, then we don't need to do anything. If the name of the user is not in the array, then we redirect the user to a different page, in my case a custom redirect page.
And that's all there is to it! Quite simple, now that I look back at it.

You'll need to have the jQuery library for SharePoint Web Services in order to get the current user, you can find it here.
Also make sure you added a reference to your script in your master page, like so:

<!--SPM:<SharePoint:ScriptLink language="javascript" ID="scriptLink9" 
 runat="server" OnDemand="false" Localizable="false" 
 name="~sitecollection/Style Library/Scripts/custom-redirect.js" />-->

You'll also need to add the following line of code directly in your master page:

<script type="text/javascript">
 window.onpaint = redirectMe();
</script>

Make sure your master page and your script are checked in. Now you can freely continue working on your site without anyone seeing that it is not yet finished! Better yet, those who you have granted full access to your site can contribute as well!

If you have any questions, feel free to ask. ;)