npm ERR: code ERESOLVE 处理方法

PS E:\VUEJS 2.6\test2\xmall> npm install -D sass-loader node-sass
npm ERR! code ERESOLVE
npm ERR! ERESOLVE could not resolve
npm ERR!
npm ERR! While resolving: element-ui@2.15.6
npm ERR! Found: vue@3.2.31
npm ERR! node_modules/vue
npm ERR!   peerOptional vue@"^2 || ^3.2.13" from @vue/babel-preset-app@5.0.4
npm ERR!     @vue/babel-preset-app@"^5.0.4" from @vue/cli-plugin-babel@5.0.4
npm ERR!     node_modules/@vue/cli-plugin-babel
npm ERR!       dev @vue/cli-plugin-babel@"~5.0.0" from the root project
npm ERR!   peer vue@"3.2.31" from @vue/server-renderer@3.2.31
npm ERR!   node_modules/@vue/server-renderer
npm ERR!     @vue/server-renderer@"3.2.31" from vue@3.2.31
npm ERR!   3 more (vue-router, vuex, the root project)
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peer vue@"^2.5.17" from element-ui@2.15.6
npm ERR! node_modules/element-ui
npm ERR!   element-ui@"^2.4.5" from the root project
npm ERR!
npm ERR! Conflicting peer dependency: vue@2.6.14
npm ERR! node_modules/vue
npm ERR!   peer vue@"^2.5.17" from element-ui@2.15.6
npm ERR!   node_modules/element-ui
npm ERR!     element-ui@"^2.4.5" from the root project
npm ERR!
npm ERR! Fix the upstream dependency conflict, or retry
npm ERR! this command with --force, or --legacy-peer-deps
npm ERR! to accept an incorrect (and potentially broken) dependency resolution.
npm ERR!
npm ERR! See C:\Users\HTADMIN\AppData\Local\npm-cache\eresolve-report.txt for a full report.
 
npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\HTADMIN\AppData\Local\npm-cache\_logs\2022-04-04T01_26_53_375Z-debug-0.log

输入npm -V发现我的npm版本为7.x的，因为npm7.x版本对某些命令比npm6.x更严格，所以莫名报了这个错

解决办法有两种：
1.在命令后加上--legacy-peer-deps
2.使用npm6.x

提示：使用npm@6不需要卸载npm@7。可以使用npx指定npm的版本。例如：npx -p npm@6 npm i --legacy-peer-deps

如果这不能立即起作用，可以先删除 node_modules和 package-lock.json