how to make a login button with jquery ?

how to make a login button with jquery ?

i have a simple index.php file which has a form with a button. When the user clicks the button  , jquery script login.js runs and alert the user. for some reason when i click the button nothing happens.


from 


  1. index.php:
  2. <!DOCTYPE html>
  3. <html>

  4. <head>

  5. <title> Log in </title>
  6. <script src = "jquery-3.1.1.js"></script>
  7. <script src = "login.js"></script>


  8. <body>


  9. <div style="width:200px;margin:auto;">
  10.      <h1> Log in Example </h1>

  11.      <p> Please log in to you raccount</p>

  12.      
  13.      <p>
  14.      <strong> Username </strong>
  15. </p>
  16. <p>
  17. <input type ="username" placeholder = "Username" >
  18. </p>
  19.  
  20.  
  21. <p>
  22.    <strong> Password</strong>
  23.  
  24.  
  25. </p>
  26.  
  27. <p>
  28.  
  29.   <input type = "password">
  30.   
  31. </p>
  32.  
  33. <button  id = "login_btn" > Log In  </button>
  34.  
  35. </div>
  36.  
  37. </body>


  38. </html>



login.js :

  1. $(document).ready(function(){

  2.    $(#login_btn").click(function(){


  3.     alert("logging in");
  4.    
  5.    
  6.    });



  7. });