How to search for just a specific file type in Visual Studio code?

You can do this.

./src/app/**/*.ts

other glob syntax

• * to match one or more characters in a path segment
• ? to match on one character in a path segment
• ** to match any number of path segments, including none
• {} to group conditions (for example {**/*.html,**/*.txt} matches all HTML and text files)
• [] to declare a range of characters to match (example.[0-9] to match on example.0, example.1, …)

Click the ellipses on the bottom right to display the "files to include" field.

You can specify a particular type with "*.filetype".

E.g.