if statement in javascript

if (hour < 18) {

    greeting = "Good day";

 } if (condition) {

  //  block of code to be executed if the condition is true

 }

 if (5 < 10) {
	console.log("5 is less than 10");
} else {
	console.log("5 is now bigger than 10")
}var age=20;
if (age < 18) {
	console.log("underage");
} else {
	console.log("let em in!");
}if (condition1) {
  //  block of code to be executed if condition1 is true
} else if (condition2) {
  //  block of code to be executed if the condition1 is false and condition2 is true
} else {
  //  block of code to be executed if the condition1 is false and condition2 is false
}if (hour < 18) {

    greeting = "Good day";

 }
else {

    greeting = "Good evening";

 }