The switch statement is used to perform different actions based on different conditions.
Use the switch statement to select one of many code blocks to be executed.
Syntax
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.
Example
getDay() method returns the weekday as a number between 0 and 6.case 0:
day = "Sunday";
break;
case 1:
day = "Monday";
break;
case 2:
day = "Tuesday";
break;
case 3:
day = "Wednesday";
break;
case 4:
day = "Thursday";
break;
case 5:
day = "Friday";
break;
case 6:
day = "Saturday";
}
The result of day will be:
SaturdayThe 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
getDay() method returns the weekday as a number between 0 and 6.If today is neither Saturday (6) nor Sunday (0), write a default message:
case 6:
text = "Today is Saturday";
break;
case 0:
text = "Today is Sunday";
break;
default:
text = "Looking forward to the Weekend";
}
The result of text will be:
Today is Saturday
The default case does not have to be the last case in a switch block:
Example
default:
text = "Looking forward to the Weekend";
break;
case 6:
text = "Today is Saturday";
break;
case 0:
text = "Today is Sunday";
}
If default is not the last case in the switch block, remember to end the default case with a break.
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
case 4:
case 5:
text = "Soon it is Weekend";
break;
case 0:
case 6:
text = "It is Weekend";
break;
default:
text = "Looking forward to the Weekend";
}
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.
In this example there will be no match for x:
Example
switch (x) {
case 0:
text = "Off";
break;
case 1:
text = "On";
break;
default:
text = "No value found";
}
Practice Excercise Practice now