JavaScript Switch Statement
The switch statement is used to perform different action based on different conditions.
The JavaScript Switch Statement
Use the switch statement to select one of many blocks of code to be executed.
Syntax
case n:
code block
break;
case n:
code block
break;
default:
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.
Example
Use today's weekday number to calculate weekday name: (Sunday=0, Monday=1, Tuesday=2, ...)
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";
break;
}
The result of day will be:
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The break Keyword
When the JavaScript code interpreter reaches a break keyword, it breaks out of the switch block.
This will stop the execution of more execution of code and/or case testing inside the block.
 |
When a match is found, and the job is done, it's time for a break. There is no need for more testing. |
|---|
The default Keyword
The default keyword specifies the code to run if there is no case match:
Example
If today is neither Saturday nor Sunday, 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:
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Common Code and Fall-Through
Sometimes, in a switch block, you will want different cases to use the same code, or fall-through to a common default.
Note from the next example, that cases can share the same code block, and that the default case does not have to be the last case in a switch block:
Example
case 1:
case 2:
case 3:
default:
text = "Looking forward to the Weekend";
break;
case 4:
case 5:
text = "Soon it is Weekend";
break;
case 0:
case 6:
text = "It is Weekend";
}
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