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const expr = "Papayas";
switch (expr) {
case "Oranges":
console.log("Oranges are $0.59 a pound.");
break;
case "Mangoes":
case "Papayas":
console.log("Mangoes and papayas are $2.79 a pound.");
// : "Mangoes and papayas are $2.79 a pound."
break;
default:
console.log(`Sorry, we are out of ${expr}.`);
}
switch (expression) {
case caseExpression1:
case caseExpression2:
//
case caseExpressionN:
default:
}
expression case
caseExpressionN expression case expression caseExpressionN case switch break
default default expression case switch default 1
switch (undefined) {
case console.log(1):
case console.log(2):
}
// 1
case default default switch default switch default default SyntaxError
switch break 2 case switch
break case default (fall-through)
const foo = 0;
switch (foo) {
case -1:
console.log("negative 1");
break;
case 0: // foo
console.log(0);
// break
case 1: // 'case 0:' break
console.log(1);
break; // break 'case 2:'
case 2:
console.log(2);
break;
default:
console.log("default");
}
// 0 1
switch switchreturn switch switch continue switch
const action = "say_hello";
switch (action) {
case "say_hello":
const message = "hello";
console.log(message);
break;
case "say_hi":
const message = "hi";
console.log(message);
break;
default:
console.log("Empty action received.");
}
"Uncaught SyntaxError: Identifier 'message' has already been declared" const message = 'hello'; 2 const message = 'hi'; case const switch
case let const
const action = "say_hello";
switch (action) {
case "say_hello": {
const message = "hello";
console.log(message);
break;
}
case "say_hi": {
const message = "hi";
console.log(message);
break;
}
default: {
console.log("Empty action received.");
}
}
hello
expr Bananas case 'Bananas' break switch switch break case 'Cherries'
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?");
default
const foo = 5;
switch (foo) {
case 2:
console.log(2);
break; // break 'default:'
default:
console.log("default");
//
case 1:
console.log("1");
}
case default
case break case
case 4
const Animal = "Giraffe";
switch (Animal) {
case "Cow":
case "Giraffe":
case "Dog":
case "Pig":
console.log("This animal is not extinct.");
break;
case "Dinosaur":
default:
console.log("This animal is extinct.");
}
case case JavaScript case
const foo = 1;
let output = "Output: ";
switch (foo) {
case 0:
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 5!");
}
foo NaN 1, 2, 3, 4, 5, 0 |
Please pick a number from 0 to 5! |
0 |
Output: So What Is Your Name? |
1 |
Output: What Is Your Name? |
2 |
Output: Your Name? |
3 |
Output: Name? |
4 |
Output: ? |
5 |
Output: ! |
if ("fetch" in globalThis) {
// fetch
} else if ("XMLHttpRequest" in globalThis) {
// XMLHttpRequest
} else {
// AJAX
}
=== switch
switch (true) {
case "fetch" in globalThis:
// fetch
break;
case "XMLHttpRequest" in globalThis:
// XMLHttpRequest
break;
default:
// AJAX
break;
}
if...else switch (true)
switch (true) {
case isSquare(shape):
console.log("This shape is a square.");
// square rectangle
case isRectangle(shape):
console.log("This shape is a rectangle.");
case isQuadrilateral(shape):
console.log("This shape is a quadrilateral.");
break;
case isCircle(shape):
console.log("This shape is a circle.");
break;
}
| ECMAScript 2027 LanguageSpecification # sec-switch-statement |
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