I have react+next and node js project and I want to deploy that project at heroku. That is the structure of my project:- 
and my package.json file is 
if I add "Start": "next start" only the frontend works and if I changed it "Start": "tsc -p server/tsconfig.json -watch && node server.js" it's gave me the error.
error is :-
Heroku安装了package.json中列出的dependencies和devDependencies之后，在运行npm start命令之前，所有devDependencies都会被删除.因此，如果您在devDependencies下安装了typescript，并且您的项目在运行时需要它，那么将找不到它.为了防止修剪，将typescript移到dependencies.
另一个选项是通过设置以下配置变量，完全跳过修剪过程:
$ heroku config:set NPM_CONFIG_PRODUCTION=false YARN_PRODUCTION=false
或者将NODE_ENV环境变量设置为production以外的任何值(Heroku的默认值).