Object.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Fuction2</title>
    <script>
      function LinksSetColor(color) {
        var alist = document.querySelectorAll("a");
        var i = 0;
        while (i < alist.length) {
          alist[i].style.color = color;
          i = i + 1;
        }
      }
      function BodySetColor(color) {
        document.querySelector("body").style.color = color;
      }
      function BodySetBackgroundColor(color) {
        document.querySelector("body").style.backgroundColor = color;
      }
      function nightDayHandler(self) {
        var target = document.querySelector("body");
        if (self.value === "night") {
          Body.setBackgroundColor("black");
          Body.setColor("white");
          self.value = "day";
          Links.setColor("powderblue");
        } else {
          Body.setBackgroundColor("white");
          Body.setColor("black");
          self.value = "night";
          Links.setColor("blue");
        }
      }
    </script>
  </head>
  <body>
    <h1><a href="index.html">신년계획</a></h1>
    <input
      id="night_day"
      type="button"
      value="night"
      onclick="nightDayhandler(this);">
    <ol>
      <li><a href="JS.html">HTML</a></li>
      <li><a href="JS2.html">CSS</a></li>
      <li><a href="JS3.html">JavaScript</a></li>
    </ol>
  </body>
</html>