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Switch statement in JavaScript | Learn basic javaScript

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DESCRIPTION

The switch statement executes a block of code depending on different cases. This is a part of JavaScript’s “Conditional” Statements, which are used to perform different actions based on different conditions. Use switch to select one of many blocks of code to be executed. This is the perfect solution for long, nested if/else statements.

How does it work ?

The switch statement evaluates an expression. The value of the expression is then compared with the values of each case in the structure. If there is a match, the associated block of code is executed.


Syntax –

switch(expression){  
case value1:  
 code to be executed;  
 break;  
case value2:  
 code to be executed;  
 break;  
......  
  
default:   
 code to be executed if above values are not matched;  
}  

Break and Default ??

The break keyword breaks out of the switch block. This will stop the execution of more execution of code and/or case testing inside the block. If break is omitted, the next code block in the switch statement is executed.

The default keyword specifies some code to run if there is no case match. There can only be one default keyword in a switch. Although this is optional, it is recommended that you use it, as it takes care of unexpected cases.

Examples of Switch

EXAMPLE 1

Use today’s weekday number to calculate the weekday name (Sunday=0, Monday=1, Tuesday=2, …) –

var day;
switch (new Date().getDay()) {
  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;
  default:
    day = "Unknown Day";
}

EXAMPLE 2

If today is neither Saturday nor Sunday, write a default message –

var text;
switch (new Date().getDay()) {
  case 6:
    text = "Today is Saturday";
    break;
  case 0:
    text = "Today is Sunday";
    break;
  default:
    text = "Looking forward to the Weekend";
}

EXAMPLE 3

Sometimes you will want different cases to use the same code, or fall-through to a common default.

var text;
switch (new Date().getDay()) {
  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";
}

The switch statement is fall-through i.e. all the cases will be evaluated if you don’t use break statement.


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