how to execute powershell ps1 scripts from package.json "scripts"?

You might set the script-shell config - either via npm config set script-shell "powershell" or environment variable $env:npm_config_script_shell="powershell"

Then you could use

"scripts": {
    "test": "Write-Host 'this is only a test'"
}

or

"scripts": {
    "buildAngular": ".\\buildAngular.ps1"
}

I'm not sure whether you can supply parameters like -NoProfile though.

Assuming powershell is in you PATH you can call it like this:

"scripts": {
    "test": "@powershell -NoProfile -ExecutionPolicy Unrestricted -Command ./test.ps1"
}

Tested on Windows 7 with Powershell v4.

Limitations are that you need Powershell installed and in your PATH. I didn't test it with Powershell for Linux, so not sure if this solution will be portable to other platform for now.