Django实现明暗主题切换遇静态文件JS空值错误求助

你遇到的Uncaught TypeError: Cannot read properties of null (reading 'querySelector')报错，核心原因是JS代码尝试对不存在的DOM元素调用querySelector方法，尽管功能能运行，但局部逻辑存在空值未判断的问题，迁移到Django模板后触发了报错。结合你的代码，具体修复方案如下：

1. 修复JS中的空值判断与变量冲突 #

你的JS代码中存在变量名重复覆盖、未判断DOM元素是否存在的问题，导致找不到对应元素时触发报错。修改后的完整JS代码如下：

}(jQuery), APP = APP || {}, function ($) {
  'use strict';

  APP.colorModes = {
    init: function () {
      this.colorModes();
    },
    colorModes: function () {
      if (!document.documentElement.hasAttribute("data-bs-theme")) return;

      // 读取并验证本地存储的主题值，确保合法
      const savedTheme = localStorage.getItem("theme");
      const getCurrentTheme = () => {
        if (savedTheme && ["light", "dark"].includes(savedTheme)) {
          return savedTheme;
        }
        return window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
      };

      const setTheme = (theme) => {
        if (theme === "auto") {
          document.documentElement.setAttribute("data-bs-theme", window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light");
        } else {
          document.documentElement.setAttribute("data-bs-theme", theme);
        }
      };

      setTheme(getCurrentTheme());

      // 更新主题切换按钮状态的函数，添加空值判断
      const updateThemeButtons = (themeValue, shouldFocus = false) => {
        const colorModesContainer = document.querySelector(".color-modes");
        if (!colorModesContainer) return;

        // 移除所有按钮的激活状态
        document.querySelectorAll("[data-bs-theme-value]").forEach(btn => {
          btn.classList.remove("active");
          btn.setAttribute("aria-pressed", "false");
        });

        document.querySelectorAll(".color-modes").forEach(container => {
          const activeIconUse = container.querySelector(".theme-icon-active use");
          const themeBtn = container.querySelector(`[data-bs-theme-value="${themeValue}"]`);
          
          // 关键：判断按钮是否存在，避免空值调用querySelector
          if (!themeBtn || !activeIconUse) return;
          
          const iconHref = themeBtn.querySelector("svg use").getAttribute("href");
          themeBtn.classList.add("active");
          themeBtn.setAttribute("aria-pressed", "true");
          activeIconUse.setAttribute("href", iconHref);
        });

        if (shouldFocus) colorModesContainer.focus();
      };

      // 监听系统主题偏好变化
      window.matchMedia("(prefers-color-scheme: dark)").addEventListener("change", () => {
        if (savedTheme !== "light" && savedTheme !== "dark") {
          setTheme(getCurrentTheme());
          updateThemeButtons(getCurrentTheme());
        }
      });

      // 绑定按钮点击事件
      const bindThemeEvents = () => {
        updateThemeButtons(getCurrentTheme());
        document.querySelectorAll("[data-bs-theme-value]").forEach(btn => {
          btn.addEventListener("click", () => {
            const theme = btn.getAttribute("data-bs-theme-value");
            localStorage.setItem("theme", theme);
            setTheme(theme);
            updateThemeButtons(theme, true);
          });
        });
      };

      bindThemeEvents();
    }
  };

  $(document).ready(function () {
    APP.colorModes.init();
  });
}

2. 确保Django模板中SVG图标资源正确加载 #

你的HTML中使用了SVG sprite（如#sun-fill），如果在Django模板中未正确引入对应的SVG资源，可能导致元素识别异常。需要在模板中添加SVG sprite定义：

{% load static %}
<!-- 隐藏的SVG Sprite容器，存放所有需要的图标 -->
<svg xmlns="http://www.w3.org/2000/svg" style="display: none;">
  <symbol id="sun-fill" viewBox="0 0 16 16">
    <path d="M8 12a4 4 0 1 0 0-8 4 4 0 0 0 0 8zM8 0a.5.5 0 0 1 .5.5v2a.5.5 0 0 1-1 0v-2A.5.5 0 0 1 8 0zm0 13a.5.5 0 0 1 .5.5v2a.5.5 0 0 1-1 0v-2A.5.5 0 0 1 8 13zm8-5a.5.5 0 0 1-.5.5h-2a.5.5 0 0 1 0-1h2a.5.5 0 0 1 .5.5zM3 8a.5.5 0 0 1-.5.5h-2a.5.5 0 0 1 0-1h2A.5.5 0 0 1 3 8zm10.657-5.657a.5.5 0 0 1 0 .707l-1.414 1.415a.5.5 0 1 1-.707-.708l1.414-1.414a.5.5 0 0 1 .707 0zm-9.193 9.193a.5.5 0 0 1 0 .707L1.05 13.657a.5.5 0 0 1-.707-.707l1.414-1.414a.5.5 0 0 1 .707 0zm9.193 2.121a.5.5 0 0 1-.707 0l-1.414-1.414a.5.5 0 0 1 .707-.707l1.414 1.414a.5.5 0 0 1 0 .707zM1.05 2.343a.5.5 0 0 1 .707 0l1.414 1.414a.5.5 0 1 1-.707.707L1.05 3.05a.5.5 0 0 1 0-.707z"/>
  </symbol>
  <symbol id="moon-stars-fill" viewBox="0 0 16 16">
    <path d="M6 .278a.768.768 0 0 1 .08.858 7.208 7.208 0 0 0-.878 3.46c0 4.021 3.278 7.277 7.318 7.277.527 0 1.04-.055 1.533-.16a.787.787 0 0 1 .81.316.733.733 0 0 1-.031.893A8.349 8.349 0 0 1 8.344 16C3.734 16 0 12.286 0 7.71 0 4.266 2.114 1.312 5.124.06A.752.752 0 0 1 6 .278z"/>
    <path d="M10.794 3.148a.217.217 0 0 1 .412 0l.387 1.162c.173.518.579.924 1.097 1.097l1.162.387a.217.217 0 0 1 0 .412l-1.162.387a1.734 1.734 0 0 0-1.097 1.097l-.387 1.162a.217.217 0 0 1-.412 0l-.387-1.162A1.734 1.734 0 0 0 9.31 6.593l-1.162-.387a.217.217 0 0 1 0-.412l1.162-.387a1.734 1.734 0 0 0 1.097-1.097l.387-1.162zM13.863.099a.145.145 0 0 1 .274 0l.258.774c.115.346.386.617.732.732l.774.258a.145.145 0 0 1 0 .274l-.774.258a1.156 1.156 0 0 0-.732.732l-.258.774a.145.145 0 0 1-.274 0l-.258-.774a1.156 1.156 0 0 0-.732-.732l-.774-.258a.145.145 0 0 1 0-.274l.774-.258c.346-.115.617-.386.732-.732L13.863.1z"/>
  </symbol>
  <symbol id="check2" viewBox="0 0 16 16">
    <path d="M13.854 3.646a.5.5 0 0 1 0 .708l-7 7a.5.5 0 0 1-.708 0l-3.5-3.5a.5.5 0 1 1 .708-.708L6.5 10.293l6.646-6.647a.5.5 0 0 1 .708 0z"/>
  </symbol>
</svg>

3. 确认Django静态资源加载顺序 #

确保JS文件在DOM渲染完成后加载：将JS引用放在模板的</body>标签前，或者通过{% block js %}在基础模板的底部引入，避免JS在DOM元素生成前执行。

{% load static %}
<!-- 页面内容 -->
<script src="{% static 'path/to/your/jquery.js' %}"></script>
<script src="{% static 'path/to/your/theme-switch.js' %}"></script>
</body>

内容的提问来源于stack exchange，提问作者Emad Younan