@push(custom-scripts') not working laravel

In laravel I'm using scripts.In view,

@push('custom-scripts')
 <script src="http://ift.tt/V757Mh"></script>
 @endpush

This is not working,But when use pushonce method instead,

It's working,and the code like

@pushonce('custom-scripts')
<script src="http://ift.tt/V757Mh"></script>
 @endpushonce

Why it's not working? How do I solve this?

via Chebli Mohamed