This project is an code example for an Answer on stackoverflow.
In this code example you can find, how to use semantic-ui with jquery in angular projects.
This solution resolves following javascript error: $(..).dropdown() is not a function
If you have no time for looking at source code, so here the short answer:
Step 1: npm install --save @types/jquery
Step 2: import 'jquery' is the right import for using jquery
Step 3: (<any>$('.ui.dropdown')).dropdown(); is the right way to call jquery dropdown function
Check out this project and open in terminal the project folder. Run ng serve and call http://localhost:4200 in browser.