npm install node-sass sass-loader --save-dev

{
test: /\.scss$/,
loaders: ['style', 'css', 'sass'v]
}

<style lang='scss' scoped>
</style>

npm install sass-resources-loader --save-dev

scss: generateLoaders('sass')

scss: generateLoaders('sass').concat(
{
loader: 'sass-resources-loader',
options: {
//你自己的scss全局文件的路径
resources: path.resolve(__dirname, '../src/style/_common.scss')
}
}
)

//当HTML的data-theme为dark时，样式引用dark
//data-theme为其他值时，就采用组件库的默认样式
//这里我只定义了两套主题方案，想要再多只需在`$themes`里加就行了
//注意一点是，每套配色方案里的key可以自定义但必须一致，不然就会混乱

$themes: (

light: (
//字体
font_color1: #414141,
font_color2: white,

//背景
background_color1: #fff,
background_color2: #f0f2f5,
background_color3: red,
background_color4: #2674e7,

//边框
border_color1: #3d414a,

),

dark: (
//字体
font_color1: #a7a7a7,
font_color2: white,

//背景
background_color1: #1b2531,
background_color2: #283142,
background_color3: #1e6ceb,
background_color4: #323e4e,

//边框
border_color1: #3d414a,

)
);

@import "./_themes.scss";

//遍历主题map
@mixin themeify {
@each $theme-name, $theme-map in $themes {
//!global 把局部变量强升为全局变量
$theme-map: $theme-map !global;
//判断html的data-theme的属性值 #{}是sass的插值表达式
//& sass嵌套里的父容器标识  @content是混合器插槽，像vue的slot
[data-theme="#{$theme-name}"] & {
@content;
}
}
}

//声明一个根据Key获取颜色的function
@function themed($key) {
@return map-get($theme-map, $key);
}

//获取背景颜色
@mixin background_color($color) {
@include themeify {
background-color: themed($color)!important;
}
}

//获取字体颜色
@mixin font_color($color) {
@include themeify {
color: themed($color)!important;
}
}

//获取边框颜色
@mixin border_color($color) {
@include themeify {
border-color: themed($color)!important;
}
}

<style lang="scss" scoped>
 @import "@/style/_handle.scss";

 .common-util {
  font-size: 18px;
  @include font_color("font_color1");
  @include background_color("background_color1");
  @include border_color("border_color1");
 }
</style>

<DropdownMenu slot="list">
 <DropdownItem @click.native="theme('iview')">默认</DropdownItem>
 <DropdownItem @click.native="theme('light')">浅色</DropdownItem>
 <DropdownItem @click.native="theme('dark')">深色</DropdownItem>
</DropdownMenu>

//换主题
theme(type) {
this.$store.commit('upDate', {themeType: type});
window.document.documentElement.setAttribute( "data-theme", type );
}
切换后会发现你的css选择器前面多了一些东西[data-theme="dark"]
[data-theme="dark"] .ivu-layout-sider,
[data-theme="dark"] .ivu-menu-light,
[data-theme="dark"] .ivu-layout-header {
background-color: #283142!important;
}