Use include and exclude to specify files / folders / globs. E.g.:

{
    "include":[
        "./folder"
    ],
    "exclude":[
        "./folder/**/*.spec.ts",
        "./folder/someSubFolder"
    ]
}

Globs

• For globs : **/* (e.g. sample usage somefolder/**/*) means all folder and any files (the extensions .ts/.tsx will be assumed and if allowJs:true so will .js/.jsx)

files option

Alternatively, you can use files to be explicit:

{
    "files":[
        "./some/file.ts"
    ]
}

But it is not recommended as you have to keep updating it. Instead use include to just add the containing folder.