Javascript 10分 + - 5分 + - 0分 + - 0分 + - <ul id = "tracklist"> <li class = "trackwrap"> <a c

10分

+ -

5分

+ -

0分

+ -

0分

+ -

    <ul id = "tracklist">
        <li class = "trackwrap">
            <a  class = "tracklink" href="https://www.link1.com">Track 1</a>
            <p class = "trackscore">10 points</p>
            <button class = "upvote" type="button">+</button>
            <button class = "downvote" type="button">-</button>
        </li>
        <li class = "trackwrap">
            <a  class = "tracklink" href="https://www.link2.com">Track 2</a>
            <p class = "trackscore">5 points</p>
            <button class = "upvote" type="button">+</button>
            <button class = "downvote" type="button">-</button>
        </li>
        <li class = "trackwrap">
            <a  class = "tracklink" href="https://www.link3.com">Track 3</a>
            <p class = "trackscore">0 points</p>
            <button class = "upvote" type="button">+</button>
            <button class = "downvote" type="button">-</button>
        </li>
        <li class = "trackwrap">
            <a  class = "tracklink" href="https://www.link4.com">Track 4</a>
            <p class = "trackscore">0 points</p>
            <button class = "upvote" type="button">+</button>
            <button class = "downvote" type="button">-</button>
        </li>
    </ul>

$(".upvote").on("click", function() {
    // ...
});
// (And similar for downvote)

$("#tracklist").on("click", ".upvote", function() {
    // ...
});
// (And similar for downvote)

var trackwrap = $(this).closest(".trackwrap");

var trackscore = trackwrap.find(".trackscore");

    <li class = "trackwrap">
        <a  class = "tracklink" href="https://www.link1.com">Track 1</a>
        <p class = "trackscore">10 points</p>
        <button class = "upvote" onclick="upvote(this)" type="button">+</button>
        <button class = "downvote" type="button">-</button>
    </li>

 function upvote(btn) {
     var parentElement = btn.parentElement;

     // use parentElement to edit DOM
     parentElement.style.color = "red";
 }

$(".upvote").click(function(){

   $(this).parent().css({"color":"#0f0"});
   // or $(this).parent().addClass("green");

});