Like a lot of people, I work with at least two editing tools in my day-to-day programming. For Java I generally use Eclipse but for JavaScript I use vscode because I think it's lightyears ahead of Eclipse's JavaScript tooling. Other people use other editors for their own reasons but if the files belong to an Eclipse workspace, you need to tell Eclipse to keep an eye out for external changes made to its own project files.
Otherwise Eclipse will simply not see changes made by other editors.
Here is a link to the Eclipse documentation that deals with this.
In Eclipse, goto Preferences->General->Workspace
On Windows, Window->Preferences->General->Workspace
On Mac, Eclipse->Preferenes->General->Workspace
Check the box for "Refresh using native hooks or polling"
