How to change bootstrap modal body content dynamically

I created a bootstrap modal, I am looking for possible solution to make my modal content change dynamically.. here is my modal

<div class="modal fade" id="signupmodal">
      <div class="modal-dialog">
      <div class="modal-content">
          <div class="modal-header">
              <h4>Sign up or log in</h4>
          </div>
          <div class="modal-body">
              <a class="btn btn-block btn-social btn-facebook btn-lg">
              <i class="fa fa-facebook"></i> Sign in with Facebook
              </a>
          <h4 style="text-align:center;"><b>OR</b></h4>
             <a class="btn btn-success btn-lg btn-block" data-toggle="modal" data-target="#loginmodal">LOG IN</a>
             <a type="button" class="btn btn-link btn-md" data-toggle="modal" >Create Account</a>
          </div>
          <div class="modal-footer">
              <button type="button" class="btn btn-danger btn-sm" data-dismiss="modal"><b>Close</b></button>
          </div>
          </div><!--modalcontent-->
      </div><!--modaldialog-->
  </div><!--modalfade -->`

when i click the log in button i want to change my modal-body content to this login form

 <form>
    <div class="form-group">
       <label for="inputEmail">Email / Username</label>
       <input class = "form-control" type="email"       id="inputEmail"placeholder="Email">
     </div>
    <div class="form-group">
       <label for="inputPassword">Password</label>
       <input class = "form-control" type="password" id="inputPassword" placeholder="Password">
       <a type="button" class="btn btn-link btn-sm">Forgot password</a>
     </div>
    <div class="form-group">
        <a type="button" class="btn btn-info btn-md">Log in</a>
      </div>
  </form>

THANK YOU SO MUCH!