error An unexpected error occurred: "EACCES: permission denied, mkdir '/app/node_modules'". code example

Example 1: Error: EACCES: permission denied, mkdir '/usr/local/lib/node_modules/typescript'

sudo chown -R $USER /usr/local/lib/node_modules

Example 2: Error: EACCES: permission denied, mkdir

add sudo , example sudo npm i nodemon -g