Often we may need to pass variables from server side to client for using it in a JavaScript file or in a global script. It's possible to write JavaScript code from server side script, for example, we may use something like this:

echo "<script>var userId = " . Auth::user()->id . ";</script>"

This will generate something like this:

<script>var userId = 1;</script>

So, we can use it in our JavaScript but if we want to pass an object we may pass it using similar approach by printing an object literal as an string, for example:

echo "<script>var obj = { id:1, username:'heera' };</script>";

It is like transforming a PHP object into <code>JavaScript</code> object from server to client side.

But, we can also use Laravel View Composer to accomplish same thing in a better way and we may pass an Eloquent model object as well, for example, if we want to pass the currently logged in user object to JavaScript as a JavaScript object, we may do this easily using a View Composer and can use it directly from any JavaScript segment in global scope or a JavaScript file.

If you don't know about View Composer then at first read about it on Laravel Website and also read this blog post to see a real use case of a View Composer on Heera.IT.

Let's see an example, we'll create a View Composer for our master layout so every time we show our Website (using master template), the template will automatically get a user object in the $user variable and will dump it as a json string which will be available on the client side as a JavaScript object. Here is the code, we may keep it in our filters.php file:

    View::composer('layouts.master', function($view) {
        $user = null;
        if(Auth::check()) {
            $user = Auth::user();
        }
        $view->with('authUser', $user);
    });

Well, we just declared our View Composer and bound it to our master layout/template and now we'll use it on our template to generate a JavaScript object to use it later on client side:

<script>var userObj = {{ $authUser or 'undefined' }}</script>
    
<!-- content -->

That's it! Now, we can use the user object from our JavaScript code directly once the page is ready. So, now we can use our authUser object in any JavaScript code as an object.

Actually, when we echo the Eloquent model object in our blade template using {{ $authUser or 'undefined' }} the eloquent object become a json string because Laravel converts any Eloquent object or a collection of objects to a json string using toJson() method when we directly return it from any route, controller or print/echo it in our view. So, the output will be something like following if we use console.log(authUser) in the browser's console:

From our View Composer we are just passing the user object (currently logged in user) and in our template file we are printing it using Blade Template syntax, which is {{ }}, that's it. If we want to return a custom object from the View Composer we may pass a custom object but if it's not Eloquent model object then we may manually convert it to json string using json_encode function.

Update:

Often I see question asked on StackOverflow about how to use/generate a URI from PHP to use it in the client in a JavaScript file. This could be accomplished using this approach, for example to generate a URI for an AJAX request we can do something like this (create a view composer):

View::composer('layouts.master', function($view) {
    $ajaxUrl = json_encode(array('url' => URL::action('getLocation')));
    $view->with('ajax', $ajaxUrl);
});

This goes to master layout in the head section:

<script>var ajax = {{ $ajax or 'undefined' }}</script>

Now it's possible to use the URI in the client side using something like this:

$.ajax({
    'url':ajax.url,
    // ...
});