Yargs 4.x.x.

app.js

var argv = require('yargs')
 .command('Hello', 'Greets the User', function(yargs){
  return yargs.options({
   name: {
    demand: true
   }
  });
})
.argv;
var command = argv._[0];

if (command === 'hello' && typeof argv.name !== 'undefined'){
 console.log('Hello '+ argv.name +' '+ argv.lastName);
}// end if
else if (command === 'hello'){
 console.log('hello world!');
}// end else

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