Full If Else Statement In javascript

let prompt  = require("prompt-sync")();

let a = prompt("whats your age?")

a = Number.parseInt(a)

let alert  = require("prompt-sync")({sigint:true});

if (a<0){

  alert("This is a valid age");

}

else if(a<9){

  alert("You Are A KID");

}  

else if(a<18 && a>=9){

  alert("You Are A Teenage Now");

}    

else {

  alert("You Can Drive");

}