after angular creation program, to add new components, but sometimes there will be “Cannot find module ‘@angular-devkit/core'” problem, the reason for this problem is the lack of @angular-devkit/core. In fact, this problem will prompt
at the time of new program creation, such as ng new newProject will appear after execution

npm WARN @angular-devkit/schematics@0.0.52 requires a peer of @angular-devkit/core@0.0.29 but none is installed. You must install peer dependencies yourself.
npm WARN @schematics/angular@0.1.17 requires a peer of @angular-devkit/core@0.0.29 but none is installed. You must install peer dependencies yourself.

in these tips are @ presents – devkit/core is not installed successfully, the need to install the prompt
solution is installed, enter the directory executing the following command

npm i --save-dev @angular-devkit/core

if again prompted @angular-devkit/core did not install successfully you need to uninstall angular-cli and reinstall angular-cli

npm uninstall -g angular-cli
npm install -g @angular/cli@latest

will solve

after reinstallation