For *.ts files:

npx prettier 'src/**/*.ts' --write

If you want target other file extensions:

npx prettier 'src/**/*.{js,ts,mjs,cjs,json}' --write

npx will cause a package to be downloaded and execute bin scripts provided by that package. The command npx prettier will cause the latest version of the prettier to be downloaded and the file ./bin/prettier.js will be executed.

npx also allows you specify which specific semantic version you want to download with the @ notation. So npx prettier runs latest, but npx prettier@2 will still run only version 2 even when prettier updates to a new major version.

See npx package docs:

npx [options] <command>[@version] [command-arg]...

and

-p, --package <package> - define the package to be installed. This defaults to the value of <command>. This is only needed for packages with multiple binaries if you want to call one of the other executables, or where the binary name does not match the package name. If this option is provided <command> will be executed as-is, without interpreting @version if it's there. Multiple --package options may be provided, and all the packages specified will be installed.

A somewhat deeper look at your question makes things a little bit weirder though. I'm unsure why you get different results when you run both commands, they should be equivalent (right now at least since 2 is the current major version).

Try printing the version string with both and see if you get a difference, that might show some additional details

npx prettier --version
npx prettier@2 --version

Both give me the same string, but that might be different depending on your cache or config.

You can do that using lint-staged:

Linting makes more sense when running before committing your code. By doing that you can ensure no errors are going into repository and enforce code style. But running a lint process on a whole project is slow and linting results can be irrelevant. Ultimately you only want to lint files that will be committed.

This project contains a script that will run arbitrary npm and shell tasks with a list of staged files as an argument, filtered by a specified glob pattern.

Install lint-staged and husky, which is required for pre-commit hooks, with this command:

npm install --save-dev lint-staged husky

Change your package.json as follows:

{
  "scripts": {
    "precommit": "lint-staged"
  },
  "lint-staged": {
    "*.js": [
      "prettier --write",
      "git add"
    ]
  }
}