JavaScript switch statement

　JavaScript Statements and Variable Declarations

switchStatements are a feature ofConditional statementOne of them, used to perform different actions under different conditions.

switchEvaluate the expression, match the expression value with the case clause, and execute the statements associated with the case, as well as the statements after the matching case.

Associated with each case labelbreakEnsure that once a matching statement is executed, the program will exit the switch and continue executing the statements after switch. If break is omitted, the program will continue executing the next statement after the switch statement.

defaultSpecify some code to be executed by default if no match is found. There can only be one default statement in switch. Although it is optional, it is recommended to use it because it can handle unexpected situations.

Use switch to select one of many code blocks to be executed. This is a perfect solution for long nested if ... else statements.

Syntax:

switch (expression) {
　　case value1:　　　//When the statement is executed
　　　//Result of expression match value1
　　　break;
　　case value2:　　　//When the statement is executed
　　　//Result of expression match value2
　　　break;
　　...
　　case valueN:　　　//When the statement is executed
　　　//Result of expression match valueN
　　　break;
　　default:　　　//Statement executed when none of the above conditions are met
　　　//These values match the value of the expression
　　　}

var city = document.querySelector("input").value;
var text;
switch (city) {
　　　case "Jaipur":
　　　text = "Jaipur is known as the Pink City";
　　　break;
　　　case "Bengaluru":
　　　text = "Bengaluru is known as the IT city";
　　　break;
　　　case "Kerala":　
　　　text = "Kerala God39;s Own Country";
　　　break;
　　　default:
　　　text = "I have never heard of that city...";
}

Browser compatibility

All browsers fully support the switch statement:

Parameter value

Technical details

More examples

Use the working day number to calculate the name of the working day (Sunday = 0, Monday = 1,) 1And so on...):

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 = "Undefined Day";
}

If you forget to use 'break', the script will start running from the conditions that match and then run the following conditions under the conditions that match:

var num = Number(document.querySelector("input").value);
var text;
switch (num) {
　　　case　1The number you entered is　1";
　　　case　2The number you entered is　2";
　　　case　3The number you entered is　3";
　　　case　4The number you entered is　4";
　　　case　5The number you entered is　5";
　　　default: text = "Default statement executed";
}

Sometimes, you may want the same code to be used for different cases, or use general code.

This is an example of a single-action switch statement where the same operation is executed for four different values:

var num = Number(document.querySelector("input").value);
var text;
switch (num) {
　　　case　1:
　　　case　2:
　　　case　3:
　　　case　4:
　　text = "The number you entered is between"　1　-　4";
　　break;
　　　case　5:
　　　case　6:
　　　case　7:
　　　case　8:
　　text = "The number you entered is between"　5　-　8";
　　break;　
　　　default: text = "Default statement executed";
}

Related References

JavaScript Tutorial:JavaScript If ... Else Statement

JavaScript Tutorial:JavaScript switch

JavaScript Reference:JavaScript break Statement

　JavaScript Statements and Variable Declarations