successively refactored jQuery code...

gistfile1.txt

.tour{
    background-color: green;
    border-radius: 10px;
}
h2{
    margin-top: 5px;
    margin-left: 15px;
}
.details{
    margin-left: 15px;
}
.highlight{
    background-color: yellow;
    
}
.on-sale{
    
}
.featured{
    
}

highlight.js

$(document).ready(function(){
  $("#filters").on("click", ".on-sale", function(){
  $(".tour").filter(".on-sale").addClass("highlight");
  $(".tour").filter(".featured").removeClass("highlight");
  });

  $("#filters").on("click", ".featured", function(){
  $(".tour").filter(".featured").addClass("highlight");
  $(".tour").filter(".on-sale").removeClass("highlight");
  });
    
  $("#filters").on("click", ".reset", function(){
  $(".tour").filter(".featured").removeClass("highlight");
  $(".tour").filter(".on-sale").removeClass("highlight");
  });
    
});

test.html

<div id="tours">
  <h1>Guided Tours</h1>
  <ul>
    <li class="usa tour on-sale" data-discount="299">
      <h2>New York, New York</h2>
      <span class="details">$1,899 for 7 nights</span>
      <button class="book">Book Now</button>
    </li>
    <li class="europe tour on-sale" data-discount="176">
      <h2>Paris, France</h2>
      <span class="details">$2,299 for 7 nights</span>
      <button class="book">Book Now</button>
    </li>
    <li class="asia tour featured" data-discount="349">
      <h2>Tokyo, Japan</h2>
      <span class="details">$3,799 for 7 nights</span>
      <button class="book">Book Now</button>
    </li>
  </ul>
  <ul id="filters">
    <li><button class="on-sale">On Sale</button></li>
    <li><button class="featured">Featured</button></li>
    <li><button class="reset">Reset</button></li>
  </ul>
</div>