Bootstrap Collapse not working properly (Hide Not working)

Your code works! but, It doesn't work properly without jquery.

<!DOCTYPE html>
<html lang="en">
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="">
  <script src=""></script>
  <script src=""></script>

<div class="container">
    <a href="#demo" data-toggle="collapse"><span class=”icon”>Collapsible</span></a>

    <div id="demo" class="collapse">
    Sample Code 


I had run into same trouble , there are many reasons for this , make sure that there are no repeated references in the page to bootstrap libraries , for me removing repeated reference worked .