If else if statement:

The if...else if... statement is the one level advance form of control statement that allows JavaScript to make correct decision out of several conditions.

Syntax:

if (expression 1) {    Statement(s) to be executed if expression 1 is true } else if (expression 2) {    Statement(s) to be executed if expression 2 is true }else if (expression 3) {    Statement(s) to be executed if expression 3 is true }else {    Statement(s) to be executed if no expression is true } }

There is nothing special about this code. It is just a series of if statements, where each if is part of the else clause of the previous statement. Statement(s) are executed based on the true condition, if none of the condition is true then else block is executed.