js does a if statement need a else statement code example

Example: JavaScript if else and else if

if (condition) {
  //  block of code to be executed if the condition is true
}
//-------------
if (hour < 18) {
  greeting = "Good day";
}
//-------------
if (condition) {
  //  block of code to be executed if the condition is true
} else {
  //  block of code to be executed if the condition is false
}
//-------------
if (hour < 18) {
  greeting = "Good day";
} else {
  greeting = "Good evening";
}
//-------------
if (time < 10) {
  greeting = "Good morning";
} else if (time < 20) {
  greeting = "Good day";
} else {
  greeting = "Good evening";
}