Laravel echo does not load

I have my main.js file, and I put it in template.blade.php:

<script src="{{ asset('site/js/main.js') }}"></script>

My main.js:

$.ajaxSetup({
        headers: {
            'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content')
        }
    });

    $(document).mouseup(function(e) 
    {
        var container = $(".to-hide");
        var container2 = $(".to-close");

        if ($(".no-close").length){

        } else {

        if (!container.is(e.target) && container.has(e.target).length === 0) 
        {
            container.hide();
        }

        if (!container2.is(e.target) && container2.has(e.target).length === 0) 
        {
            container2.remove();
        }
        }
    });

     //import Echo from 'laravel-echo'

     window.Pusher = require('pusher-js');

     window.Echo = new Echo({
         broadcaster: 'pusher',
         key: 'MY-KEY'
     });

When I remove the comment from //import Echo from 'laravel-echo' jquery and js from the file stops running, and probably is not importing laravel-echo. What can it be?

Return this to the console on the line:

  

Uncaught SyntaxError: Unexpected identifier

I've tried adding js / bootstrap.js also gives the same error.