Yeoman Environment 
Yeoman Environment is responsible of handling the lifecyle and bootstrap of generators in a specific environment (your app).
It provides a high-level API to discover, create and run generators, as well as further tuning where and how a generator is resolved.
Usage
var yeoman = require('yeoman-generator');
var env = yeoman.createEnv();
// The #lookup() method will search the user computer for installed generators. The search
// if done from the current working directory.
env.lookup(function () {
env.run('angular', { 'skip-install': true }, done);
});For advance usage, see our API documentation