有时候一个项目的主题并不能满足所有人的审美，这时候换肤功能就很友好，本项目基于vue+element实现后台管理项目的换肤功能

1.创建换肤组件

<template>
  <el-color-picker
    class="theme-picker"
    popper-class="theme-picker-dropdown"
    v-model="theme"
    :predefine="predefineColors"
  ></el-color-picker>
</template>

<script>
const version = require("element-ui/package.json").version; // element-ui version from node_modules
const ORIGINAL_THEME = "#409EFF"; // default color
export default {
  name: "ThemePicker",
  props: {
    default: {
      // 初始化主题，可由外部传入
      type: String
      // default: '#2668b1'
      // default: `${localStorage.getItem("tremePackers")==null?"#C60404":localStorage.getItem("tremePackers")}`
    }
    // size: { // 初始化主题，可由外部传入
    //   type: String,
    //   default: 'small'
    // },
  },
  data() {
    return {
      chalk: "", // content of theme-chalk css
      theme: ORIGINAL_THEME,
      showSuccess: true, // 是否弹出换肤成功消息
      predefineColors: [
        "#2668b1",
        "#52b493",
        "#429798",
        "#32789c",
        "#1944a5",
        "#5944bc",
        "#995dcd",
        "#ce7e5b",
        "#ee8b9b",
        "#283551"
      ]
    };
  },
  mounted() {
    this.theme = this.defaultTheme;
    // this.$emit('onThemeChange', this.theme)
    this.showSuccess = true;
  },
  computed: {
    defaultTheme() {
      return this.$store.state.theme;
    }
  },
  watch: {
    async theme(val, oldVal) {
          if (typeof val !== "string") return;
          const themeCluster = this.getThemeCluster(val.replace("#", ""));
          const originalCluster = this.getThemeCluster(oldVal.replace("#", ""));
          const getHandler = (variable, id) => {
            return () => {
              const originalCluster = this.getThemeCluster(
                ORIGINAL_THEME.replace("#", "")
              );
              const newStyle = this.updateStyle(
                this[variable],
                originalCluster,
                themeCluster
              );

              let styleTag = document.getElementById(id);
              if (!styleTag) {
                styleTag = document.createElement("style");
                styleTag.setAttribute("id", id);
                // document.head.appendChild(styleTag)
                document
                  .getElementsByTagName("style")[0]
                  .insertBefore(styleTag, null);
              }
              styleTag.innerText = newStyle;
            };
          };

          const chalkHandler = getHandler("chalk", "chalk-style");

          if (!this.chalk) {
            const url = `../../assets/style/theme/index.css`;//本地css样式地址
            // const url = `./dist/index.css`;//项目打包后css地址（原文件放入public文件夹中）
            // const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`;//如果是公司内网，此网址则不适用
            this.getCSSString(url, chalkHandler, "chalk");

          } else {
            chalkHandler();
          }

          const styles = [].slice
            .call(document.querySelectorAll("style"))
            .filter(style => {
              const text = style.innerText;
              return (
                new RegExp(oldVal, "i").test(text) &&
                !/Chalk Variables/.test(text)
              );
            });
          styles.forEach(style => {
            const { innerText } = style;
            if (typeof innerText !== "string") return;
            style.innerText = this.updateStyle(
              innerText,
              originalCluster,
              themeCluster
            );
          });
          this.$store.commit("themColor", val);//将更换的颜色存入store
          this.$emit("onThemeChange", val);

        // 响应外部操作

        //存入localStorage
        // localStorage.setItem('tremePackers',val);
        // if(this.showSuccess) {
        //   this.$message({
        //     message: '换肤成功',
        //     type: 'success'
        //   })
        // } else {
        //   this.showSuccess = true
        // }
      
    }
  },
  methods: {
    updateStyle(style, oldCluster, newCluster) {
      let newStyle = style;
      oldCluster.forEach((color, index) => {
        newStyle = newStyle.replace(new RegExp(color, "ig"), newCluster[index]);
      });
      return newStyle;
    },
    
    getCSSString(url, callback, variable) {
      const xhr = new XMLHttpRequest();
      xhr.onreadystatechange = () => {
        if (xhr.readyState === 4 && xhr.status === 200) {
          this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, "");
          callback();
        }
      };
      xhr.open("GET", url);
      xhr.send();
    },

    getThemeCluster(theme) {
      const tintColor = (color, tint) => {
        let red = parseInt(color.slice(0, 2), 16);
        let green = parseInt(color.slice(2, 4), 16);
        let blue = parseInt(color.slice(4, 6), 16);

        if (tint === 0) {
          // when primary color is in its rgb space
          return [red, green, blue].join(",");
        } else {
          red += Math.round(tint * (255 - red));
          green += Math.round(tint * (255 - green));
          blue += Math.round(tint * (255 - blue));

          red = red.toString(16);
          green = green.toString(16);
          blue = blue.toString(16);

          return `#${red}${green}${blue}`;
        }
      };

      const shadeColor = (color, shade) => {
        let red = parseInt(color.slice(0, 2), 16);
        let green = parseInt(color.slice(2, 4), 16);
        let blue = parseInt(color.slice(4, 6), 16);

        red = Math.round((1 - shade) * red);
        green = Math.round((1 - shade) * green);
        blue = Math.round((1 - shade) * blue);

        red = red.toString(16);
        green = green.toString(16);
        blue = blue.toString(16);

        return `#${red}${green}${blue}`;
      };

      const clusters = [theme];
      for (let i = 0; i <= 9; i++) {
        clusters.push(tintColor(theme, Number((i / 10).toFixed(2))));
      }
      clusters.push(shadeColor(theme, 0.1));
      return clusters;
    }
  }
};
</script>

<style>
.theme-picker .el-color-picker__trigger {
  vertical-align: middle;
}

.theme-picker-dropdown .el-color-dropdown__link-btn {
  display: none;
}
.el-color-picker--small .el-color-picker__trigger {
  border: none;
}
</style>

上面这块代码值得注意，红框里的代码是在head里所有节点后插入一个新的style标签，打包后优先级较高，但有个问题，有些地方的颜色直接消失变成空白影响了样式，于是改成绿框里的代码，但绿框里的代码打包后优先级会低于原来样式颜色的而优先级，所以需要根据项目调样式优先级

这块的代码也需要注意，如果公司直接使用的外网那么直接使用第三个url就行，如果公司使用的内网访问不了外部网页那么可以通过第三条url下载项目对应element版本的css样式,把css文件放到项目里，但要注意放到不会被编译的问价夹里，我项目用的是vue cli4,所以我动态转换的css文件放在public文件夹里，放到assets问价夹中样式文件会被编译，因而路径会报404，并且这块使用的url是文件打包编译后样式的路径，这是值得注意的地方

2.如果项目中有的样式颜色没有用到element，可以把颜色缓存到vuex里，然后在具体逐渐里通过计算属性获取再在样式上动态绑定

vuex：

使用的组件中：