JavaScript Switch Statement

The switch statement is used to perform different actions based on different conditions.

Syntax:

switch(expression) {

  case x:

    // code block

    break;

  case y:

    // code block

    break;

  default:

    // code block

}

This is how it works:

The switch expression is evaluated once.

The value of the expression is compared with the values of each case.

If there is a match, the associated block of code is executed.

If there is no match, the default code block is executed.

The getDay() method returns the weekday as a number between 0 and 6.

(Sunday=0, Monday=1, Tuesday=2 ..)

This example uses the weekday number to calculate the weekday name:

EXAMPLE ❯


The break Keyword

When JavaScript reaches a break keyword, it breaks out of the switch block.

This will stop the execution inside the switch block.

It is not necessary to break the last case in a switch block. The block breaks (ends) there anyway.

Note: If you omit the break statement, the next case will be executed even if the evaluation does not match the case.


The default Keyword

The default keyword specifies the code to run if there is no case match:

Example:

The getDay() method returns the weekday as a number between 0 and 6.

If today is neither Saturday (6) nor Sunday (0), write a defult message:

If default is not the last case in the switch block, remember to end the default case with a break.

EXAMPLE ❯


Common Code Blocks

Sometimes you will want different switch cases to use the same code.

In this example case 4 and 5 share the same code block, and 0 and 6 share another code block:

EXAMPLE ❯


Switching Details

If multiple cases matches a case value, the first case is selected.

If no matching cases are found, the program continues to the default label.

If no default label is found, the program continues to the statement(s) after the switch.


Strict Comparison

Switch cases use strict comparison (===).

The values must be of the same type to match.

A strict comparison can only be true if the operands are of the same type.

EXAMPLE ❯