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The switch
statement evaluates an expression, matching the expression's value to a case
clause, and executes statements associated with that case, as well as statements in cases that follow the matching case.
The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
Syntax
switch (expression) { case value1: //Statements executed when the //result of expression matches value1 [break;] case value2: //Statements executed when the //result of expression matches value2 [break;] ... case valueN: //Statements executed when the //result of expression matches valueN [break;] [default: //Statements executed when none of //the values match the value of the expression [break;]] }
expression
- An expression whose result is matched against each case clause.
case valueN
Optional- A
case
clause used to match againstexpression
. If theexpression
matches the specifiedvalueN
, the statements inside the case clause are executed until either the end of theswitch
statement or abreak
. default
Optional- A
default
clause; if provided, this clause is executed if the value ofexpression
doesn't match any of thecase
clauses.
Description
A switch statement first evaluates its expression. It then looks for the first case
clause whose expression evaluates to the same value as the result of the input expression (using the strict comparison, ===
) and transfers control to that clause, executing the associated statements. (If multiple cases match the provided value, the first case that matches is selected, even if the cases are not equal to each other.)
If no matching case
clause is found, the program looks for the optional default
clause, and if found, transfers control to that clause, executing the associated statements. If no default
clause is found, the program continues execution at the statement following the end of switch
. By convention, the default
clause is the last clause, but it does not need to be so.
The optional break
statement associated with each case label ensures that the program breaks out of switch once the matched statement is executed and continues execution at the statement following switch. If break
is omitted, the program continues execution at the next statement in the switch
statement.
Examples
Using switch
In the following example, if expr
evaluates to "Bananas", the program matches the value with case "Bananas" and executes the associated statement. When break
is encountered, the program breaks out of switch
and executes the statement following switch
. If break
were omitted, the statement for case "Cherries" would also be executed.
switch (expr) { case 'Oranges': console.log('Oranges are $0.59 a pound.'); break; case 'Apples': console.log('Apples are $0.32 a pound.'); break; case 'Bananas': console.log('Bananas are $0.48 a pound.'); break; case 'Cherries': console.log('Cherries are $3.00 a pound.'); break; case 'Mangoes': case 'Papayas': console.log('Mangoes and papayas are $2.79 a pound.'); break; default: console.log('Sorry, we are out of ' + expr + '.'); } console.log("Is there anything else you'd like?");
What happens if I forgot a break?
If you forget a break then the script will run from the case where the criterion is met and will run the case after that regardless if criterion was met. See example here:
var foo = 0; switch (foo) { case -1: console.log('negative 1'); break; case 0: // foo is 0 so criteria met here so this block will run console.log(0); // NOTE: the forgotten break would have been here case 1: // no break statement in 'case 0:' so this case will run as well console.log(1); break; // it encounters this break so will not continue into 'case 2:' case 2: console.log(2); break; default: console.log('default'); }
Can I put a default between cases?
Yes, you can! JavaScript will drop you back to the default if it can't find a match:
var foo = 5; switch (foo) { case 2: console.log(2); break; // it encounters this break so will not continue into 'default:' default: console.log('default') // fall-through case 1: console.log('1'); }
It also works when you put default before all other cases.
Methods for multi-criteria case
Source for this technique is here:
Switch statement multiple cases in JavaScript (Stack Overflow)
Multi-case - single operation
This method takes advantage of the fact that if there is no break below a case statement it will continue to execute the next case statement regardless if the case meets the criteria. See the section titled "What happens if I forgot a break?"
This is an example of a single operation sequential switch statement, where four different values perform exactly the same.
var Animal = 'Giraffe'; switch (Animal) { case 'Cow': case 'Giraffe': case 'Dog': case 'Pig': console.log('This animal will go on Noah\'s Ark.'); break; case 'Dinosaur': default: console.log('This animal will not.'); }
Multi-case - chained operations
This is an example of a multiple-operation sequential switch statement, where, depending on the provided integer, you can receive different output. This shows you that it will traverse in the order that you put the case statements, and it does not have to be numerically sequential. In JavaScript, you can even mix in definitions of strings into these case statements as well.
var foo = 1; var output = 'Output: '; switch (foo) { case 10: output += 'So '; case 1: output += 'What '; output += 'Is '; case 2: output += 'Your '; case 3: output += 'Name'; case 4: output += '?'; console.log(output); break; case 5: output += '!'; console.log(output); break; default: console.log('Please pick a number from 0 to 6!'); }
The output from this example:
Value | Log text |
---|---|
foo is NaN or not 1, 2, 3, 4, 5 or 10 | Please pick a number from 0 to 6! |
10 | Output: So What Is Your Name? |
1 | Output: What Is Your Name? |
2 | Output: Your Name? |
3 | Output: Name? |
4 | Output: ? |
5 | Output: ! |
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 3rd Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.2 |
ECMAScript 5.1 (ECMA-262) The definition of 'switch statement' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'switch statement' in that specification. |
Standard | |
ECMAScript Latest Draft (ECMA-262) The definition of 'switch statement' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | Yes | Yes | 1 | Yes | Yes | Yes |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | Opera Android | iOS Safari | Samsung Internet |
---|---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | 4 | Yes | Yes | Yes |