Error : Cannot read properties of null (reading 'classList')

Question

要复制，请单击 svg，然后单击右上角的红色 X。

继续这样做，直到出现错误。

https://jsfiddle.net/qv8k59jc/

如何修复代码并消除错误？

代码中更改或添加了什么？

在代码片段中也出现了错误。

该错误是如何解决的？

这就是我想要做的。

它是如何工作的，你点击 svg，然后点击 X 退出页面。

每次单击红色 x 退出页面时，我都会收到该错误消息。

const manageCover = (function makeManageCover() {
  const config = {};

  function show(el) {
    el.classList.remove("hide");
  }

  function hide(el) {
    el.classList.add("hide");
  }

  function hideAll(elements) {
    elements.forEach(hide);
  }

  function showCovers(playButton) {
    const cover = playButton.parentElement;
    cover.classList.add("active");
    show(cover);
  }

  function coverClickHandler(evt) {
    hideAll(config.containers);
    const cover = evt.currentTarget;
    showCovers(cover);
  }

  function homeClickHandler(evt) {

    const home = evt.currentTarget;
    showHome(home);
  }

  function showHome(el) {
    const theActive = document.querySelector(".with-curtain.active");
    const theHides = document.querySelectorAll(".hide");
    const theBody = document.querySelector("body");
    theActive.classList.remove("active");

    theHides.forEach(function (removeHide) {
      removeHide.classList.remove("hide");
    });

    void theBody.offsetWidth; //restart animation
    theBody.classList.toggle("bodytoggle");

  }

  function addClickToButtons(playButtons) {
    playButtons.forEach(function addEventHandler(playButton) {
      playButton.addEventListener("click", coverClickHandler);
    });
  }

  function addClickToHome(goHome) {
    goHome.forEach(function addEventHandler(goHome) {
      goHome.addEventListener("click", homeClickHandler);
    });
  }

  function addCoverHandler(coverSelector, handler) {
    const cover = document.querySelector(coverSelector);
    cover.addEventListener("click", handler);
  }


  function init(selectors) {
    config.containers = document.querySelectorAll(selectors.container);
    const playButtons = document.querySelectorAll(selectors.playButton);
    addClickToButtons(playButtons);
    const goHome = document.querySelectorAll('.home');
    addClickToHome(goHome);

  }

  return {
    addCoverHandler,
    init,
    show
  };
}());

const videoPlayer = (function makeVideoPlayer() {
  const players = [];

  const tag = document.createElement("script");
  tag.src = "https://www.youtube.com/player_api";
  const firstScriptTag = document.getElementsByTagName("script")[0];
  firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);

  function onPlayerReady(event) {
    const player = event.target;
    player.setVolume(100); // percent
  }


  function addPlayer(video, settings, videoIds = video.dataset.id) {
    const videoId = !Array.isArray(videoIds) && videoIds;
    const playlist = Array.isArray(videoIds) && videoIds.join();
    const defaults = {
      playerOptions: {
        events: {
          "onReady": onPlayerReady
        },
        height: 360,
        host: "https://www.youtube-nocookie.com",
        playerVars: {
          playlist: playlist || undefined
        },
        videoId,
        width: 640
      }
    };

    const defaultOptions = defaults.playerOptions;
    const defaultVars = defaultOptions.playerVars;
    const playerVars = settings.playerVars;
    const playerOptions = Object.assign({}, defaultOptions, settings);
    playerOptions.playerVars = Object.assign({}, defaultVars, playerVars);
    const player = new YT.Player(video, playerOptions);
    players.push(player);
    return player;
  }

  return {
    addPlayer
  };
}());

const managePlayer = (function makeManagePlayer() {
  const defaults = {
    playerOptions: {
      playerVars: {
        autoplay: 1,
        controls: 0,
        disablekb: 1,
        enablejsapi: 1,
        fs: 0,
        iv_load_policy: 3,
        rel: 0
      }
    }
  };

  function show(el) {
    el.classList.remove("hide");
  }

  function createPlayerOptions(settings) {
    const defaultOptions = defaults.playerOptions;
    const playerOptions = defaultOptions.playerVars;
    const playerVars = Object.assign({}, playerOptions, settings);
    playerOptions.playerVars = playerVars;
    return playerOptions;
  }

  function createPlayer(videoWrapper, settings = {}, videoIds = "") {
    const video = videoWrapper.querySelector(".video");
    if (!videoIds) {
      videoIds = video.dataset.id;
    }
    const playerOptions = createPlayerOptions(settings);
    return videoPlayer.addPlayer(video, playerOptions, videoIds);
  }

  function createCoverClickHandler(playerSettings, videoIds) {
    return function coverClickHandler(evt) {
      const cover = evt.currentTarget;
      const wrapper = cover.nextElementSibling;
      show(wrapper);
      const player = createPlayer(wrapper, playerSettings, videoIds);
      wrapper.player = player;
    };
  }

  function addPlayer(coverSelector, playerSettings, videoIds) {
    const clickHandler = createCoverClickHandler(playerSettings, videoIds);
    manageCover.addCoverHandler(coverSelector, clickHandler);
  }


  function addPlayerRandomVideo(coverSelector, playerSettings, videoIds) {
    const index = Math.floor(Math.random() * videoIds.length);
    const videoId = videoIds[index];
    const clickHandler = createCoverClickHandler(playerSettings, videoId);
    manageCover.addCoverHandler(coverSelector, clickHandler);
  }

  function init(playerOptions) {
    Object.assign(defaults.playerOptions, playerOptions);
  }

  return {
    add: addPlayer,
    addRandom: addPlayerRandomVideo,
    init
  };
}());

function onYouTubeIframeAPIReady() {
  managePlayer.init({
    playerVars: {
      controls: 1,
      fs: 0
    }
  });
  managePlayer.addRandom(".playa", {
    start: 45
  }, [
    "0dgNc5S8cLI",
    "mnfmQe8Mv1g",
    "-Xgi_way56U",
    "CHahce95B1g"
  ]);
  managePlayer.add(".playb", {}, [
    "0dgNc5S8cLI",
    "mnfmQe8Mv1g",
    "-Xgi_way56U",
    "CHahce95B1g"
  ]);
  managePlayer.add(".playc", {
    start: 45
  });
  manageCover.init({
    container: ".container",
    playButton: ".thePlay"
  });
}

html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

body {
  background: #353198;
  animation: fade 2s ease 0s forwards;
}

.bodytoggle{
  animation:fade2 2s ease forwards;
}

@keyframes fade {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}

@keyframes fade2 {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}
.outer {
  display: flex;
  min-height: 100%;
  box-sizing: border-box;
  justify-content: center;
}
.container {
  display: flex;
  justify-content: center;
}
.container.active {
  flex: 1 0 0;
  animation: fadebody 5s ease 0s forwards;
  background-size: 165px 165px;
  background-image: linear-gradient(teal 5px, #0000 5px),
    linear-gradient(90deg, teal 5px, #0000 5px),
    linear-gradient(black 10px, #0000 10px 160px, black 160px),
    linear-gradient(90deg, black 10px, #0000 10px 160px, black 160px),
    linear-gradient(orange 15px, #0000 15px 155px, orange 155px),
    linear-gradient(90deg, orange 15px, #0000 15px 155px, orange 155px),
    linear-gradient(black 20px, #0000 20px 150px, black 150px),
    linear-gradient(90deg, black 20px, #0000 20px 150px, black 150px),
    linear-gradient(teal 25px, #0000 25px 145px, teal 145px),
    linear-gradient(90deg, teal 25px, #0000 25px 145px, teal 145px),
    linear-gradient(black 30px, #0000 30px 140px, black 140px),
    linear-gradient(90deg, black 30px, #0000 30px 140px, black 140px),
    linear-gradient(orange 35px, #0000 35px 135px, orange 135px),
    linear-gradient(90deg, orange 35px, #0000 35px 135px, orange 135px),
    linear-gradient(black 40px, #0000 40px 130px, black 130px),
    linear-gradient(90deg, black 40px, #0000 40px 130px, black 130px),
    linear-gradient(teal 45px, #0000 45px 125px, teal 125px),
    linear-gradient(90deg, teal 45px, #0000 45px 125px, teal 125px),
    linear-gradient(black 50px, #0000 50px 120px, black 120px),
    linear-gradient(90deg, black 50px, #0000 50px 120px, black 120px),
    linear-gradient(orange 55px, #0000 55px 115px, orange 115px),
    linear-gradient(90deg, orange 55px, #0000 55px 115px, orange 115px),
    linear-gradient(black 60px, #0000 60px 110px, black 110px),
    linear-gradient(90deg, black 60px, #0000 60px 110px, black 110px),
    linear-gradient(teal 65px, #0000 65px 105px, teal 105px),
    linear-gradient(90deg, teal 65px, #0000 65px 105px, teal 105px),
    linear-gradient(black 70px, #0000 70px 100px, black 100px),
    linear-gradient(90deg, black 70px, #0000 70px 100px, black 100px),
    linear-gradient(orange 75px, #0000 75px 95px, orange 95px),
    linear-gradient(90deg, orange 75px, #0000 75px 95px, orange 95px),
    linear-gradient(black 80px, #0000 80px 90px, black 90px),
    linear-gradient(90deg, black 80px, #0000 80px 90px, black 90px),
    linear-gradient(teal, teal);
}
/* when container is active hide the svg */
.container.active .thePlay {
  display: none;
}

.inner-container {
  display: none;
}
/* when container is active hide the svg and show the inner container*/
.container.active .thePlay {
  display: none;
}
.container.active .inner-container {
  display: flex;
}
.container.active .inner-container.curtain {
  display: block;
}

@keyframes fadebody {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}

.playa,
.playb,
.playc {
  margin: auto 20px;
  width: 90px;
  height: 90px;
  border-radius: 50%;
  cursor: pointer;
  flex-shrink: 0;
}

.playa {
  fill: red;
  filter: drop-shadow(3px 3px 3px rgba(0, 0, 0, 0.7));
}

.playb {
  fill: blue;
  filter: drop-shadow(3px 3px 3px rgba(0, 0, 0, 0.7));
}

.playc {
  fill: orange;
  filter: drop-shadow(3px 3px 3px rgba(0, 0, 0, 0.7));
}

svg.thePlay {
 pointer-events: none;
}

 .home {
  position: fixed;
  top: 0;
  right: 0;
  cursor: pointer;
  width: 50px;
  height: 50px;
  background: black;
}

.home::before,
.home::after {
  content: "";
  background-color: #d4001e;
  width: 40px;
  height: 8px;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  margin:auto;
}

.home::before {
  transform: rotate(45deg);
}

.home::after {
  transform: rotate(-45deg);
}



.curtain {
  position: relative;
  max-width: 640px;
  margin: auto;
  flex: 1 0 0%;
}
.panel-left,
.panel-right {
  position: absolute;
  height: 100%;
  width: calc(50% + 1px); /* rounding error fix */
  top: 0%;
  transition: all ease 10s;

  /*background-image: url("https://picsum.photos/600");
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center;*/
  overflow: hidden;
}

.panel-left {
  left: 0;
  /*background-color: rgb(91, 96, 106);*/
}

.panel-right {
  right: 0;
  /*background-color: rgb(229, 211, 211);*/
}

.panel-left::before,
.panel-right::before {
  content: "";
  position: absolute;
  height: 100%;
  width: 200%;
  top: 0;
  left: 0;
  background-image: url("https://picsum.photos/id/26/1920/1080");
  background-size: auto;
  background-repeat: no-repeat;
  background-position: 0 0;
}
.curtain2 .panel-left::before,
.curtain2 .panel-right::before {
  background-image: url("https://picsum.photos/id/27/1920/1080");
}

.panel-right::before {
  left: -100%;
}

.container.active .curtain .panel-left {
  animation: curtain1 8s forwards;
  animation-delay: 1s;
}

@keyframes curtain1 {
  to {
    transform: translateX(-100%);
  }
}

.container.active .curtain .panel-right {
  animation: curtain2 8s forwards;
  animation-delay: 1s;
}

@keyframes curtain2 {
  to {
    transform: translateX(100%);
  }
}

.ratio-keeper {
  position: relative;
  height: 0;
  padding-top: 56.25%;
  border-radius: 25px;
  margin: auto;
  overflow: hidden;
}

.video-frame {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

.hide {
  display: none;
}

<div class="outer">
   <div class="container with-curtain">
      <svg class="playa thePlay" width="64" height="64" viewBox="0 0 64 64" pointer-events="none">
         <g id="play">
            <title>Play</title>
            <circle cx="32" cy="32" r="32" fill="transparent" pointer-events="visiblePainted" />
            <path d="M25.6,46.4L44.8,32L25.6,17.6V46.4z M32,0C14.3,0,0,14.3,0,32s14.3,32,32,32s32-14.3,32-32S49.7,0,32,0z
               M32,57.6C17.9,57.6,6.4,46.1,6.4,32S17.9,6.4,32,6.4S57.6,17.9,57.6,32S46.1,57.6,32,57.6z" />
         </g>
      </svg>
      <div class="inner-container curtain curtain1">
         <div class="ratio-keeper">
            <div class="wrapa">
               <div class="video video-frame"></div>
            </div>
            <div class="panel-left"></div>
            <div class="panel-right"></div>
         </div>
         <div class="home"><button class="home" aria-label="Close"></button></div>
      </div>
   </div>
   <div class="container with-curtain">
      <svg class="playb thePlay" width="100%" height="100%" viewBox="0 0 64 64">
         <use href="#play" />
      </svg>
      <div class="inner-container curtain curtain2">
         <div class="ratio-keeper">
            <div class="wrapa">
               <div class="video video-frame"></div>
            </div>
            <div class="panel-left"></div>
            <div class="panel-right"></div>
         </div>
         <div class="home"><button class="home" aria-label="Close"></button></div>
      </div>
   </div>
   <div class="container with-curtain">
      <svg class="playc thePlay" width="100%" height="100%" viewBox="0 0 64 64">
         <use href="#play" />
      </svg>
      <div class="inner-container curtain curtain3">
         <div class="ratio-keeper">
            <div class="wrapa">
               <div class="video video-frame" data-id="qe5WF4qCSkQ"></div>
            </div>
            <div class="panel-left"></div>
            <div class="panel-right"></div>
         </div>
         <div class="home"><button class="home" aria-label="Close"></button></div>
      </div>
   </div>
</div>

Answer 1

由于 'null' 来自变量 'theActive'[=21 的空文档查询选择器，您收到异常=].您可以通过在 showHome 方法的第 38 行添加以下内容来找到罪魁祸首：

console.log(theActive == null, theHides == null, theBody == null);

控制台输出：

false, false, false true, false, false

Error : Cannot read properties of null (reading 'classList')

Error : Cannot read properties of null (reading 'classList')

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