“mockjs“ is already in “devDependencies“. Please remove existing entry first before adding it to “de

提示说你下的依赖已经存在mockjs了，你又重新下了一个冲突了，解决的话，就是卸载mockjs,然后重新下载就行了

npm

卸载依赖
npm uninstall  mockjs

安装依赖
npm uninstall  mockjs

yarn

卸载依赖
yarn remove  mockjs

安装依赖
yarn add  mockjs