is-path-in-cwd 
Check if a path is in the current working directory
Install
$ npm install --save is-path-in-cwd
Usage
var isPathInCwd = require('is-path-in-cwd');
isPathInCwd('unicorn');
//=> true
isPathInCwd('../rainbow');
//=> false
isPathInCwd('.');
//=> false
License
MIT © Sindre Sorhus