应完整修改为:
<el-button type="primary" icon="el-icon-plus" @click="addUser">新增用户</el-button>.el-button--primary:not(.is-disabled) {background-color: #1174de;border-color: #1174de;&:hover {&:not(.is-disabled) {opacity: 0.8;}&:active {opacity: 1;}}}
注意:.el-button--primary:后要增加not(.is-disabled),否则disabled状态下也有完整透明度的背景色
存疑:为什么&:active在&:hover内才生效?