can we pass if else statement for html from nodejs code example

Example 1: javascript if else

var age=20;
if (age < 18) {
	console.log("underage");
} else {
	console.log("let em in!");
}

Example 2: elif exist in js?

switch (true) {
  case condition1:
     //e.g. if (condition1 === true)
     break;
  case condition2:
     //e.g. elseif (condition2 === true)
     break;
  default:
     //e.g. else
}