The
switchstatement is used to perform different actions based on different conditions.
switchмэдэгдэл нь янз бүрийн нөхцөлд үндэслэн янз бүрийн үйлдлийг хийхэд хэрэглэгддэг.
The JavaScript Switch Statement #
Use the switch statement to select one of many code blocks to be executed.
switch -ийг ашиглан олон кодын блокуудын аль нэгийг сонгоно уу.
Syntax Синтакс #
switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}
This is how it works:
Энэ нь хэрхэн ажиллах вэ:
- The switch expression is evaluated once.
Шилжүүлэгчийн илэрхийлэлийг нэг удаа үнэлнэ.
- The value of the expression is compared with the values of each case.
Илэрхийллийн утгыг тохиолдол бүрийн утгатай харьцуулна.
- If there is a match, the associated block of code is executed.
Хэрэв таарч байвал холбогдох кодын блокыг гүйцэтгэнэ.
- If there is no match, the default code block is executed.
Хэрэв тохирох зүйл байхгүй бол анхдагч кодын блокыг гүйцэтгэнэ.
Example Жишээ #
The getDay() method returns the weekday as a number between 0 and 6.
getDay() арга нь ажлын өдрийг 0-6 хоорондох тоогоор буцаана.
(Sunday=0, Monday=1, Tuesday=2 ..)
This example uses the weekday number to calculate the weekday name:
Энэ жишээнд ажлын өдрийн нэрийг тооцоолохдоо ажлын өдрийн дугаарыг ашиглана.
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";
}
The result of day will be:
Thursday 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 default message:
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";
} The result of text will be:
Looking forward to the Weekend
The default case does not have to be the last case in a switch block:
Example #
switch (new Date().getDay()) {
default:
text = "Looking forward to the Weekend";
break;
case 6:
text = "Today is Saturday";
break;
case 0:
text = "Today is Sunday";
} switch (new Date().getDay()) {
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 #
var x = "0";
switch (x) {
case 0:
text = "Off";
break;
case 1:
text = "On";
break;
default:
text = "No value found";
} 
