Concept

Switch is a control structure in the JavaScript programming language that allows you to test a variable or an expression against multiple different values and perform corresponding actions.

Syntax

The syntax of switch consists of the following parts:

switch (biến) {
  case giá_trị_1:
    // Hành động khi biến có giá trị là giá_trị_1
    break;
  case giá_trị_2:
    // Hành động khi biến có giá trị là giá_trị_2
    break;
  ...
  default:
    // Hành động khi không có trường hợp nào khớp với giá trị của biến
}

Where:

• variable is an expression or variable to be checked.
• value_1, value_2, ... are the values that the variable can have.
• Each case represents a value to be checked and the corresponding actions.
• break is used to exit the switch after performing the actions in a case.
• default is a final case, executed if no case matches the value of the variable.

Example with code

Here is an example of how to use switch in JavaScript:

let day = "Monday";
let message;

switch (day) {
  case "Monday":
    message = "Today is Monday.";
    break;
  case "Tuesday":
    message = "Today is Tuesday.";
    break;
  case "Wednesday":
    message = "Today is Wednesday.";
    break;
  case "Thursday":
    message = "Today is Thursday.";
    break;
  case "Friday":
    message = "Today is Friday.";
    break;
  default:
    message = "Today is a weekend day.";
}

console.log(message);

The output will be "Today is Monday." because the variable day has a value of "Monday".

You can also use numbers or expressions in the cases, for example:

let number = 5;
let result;

switch (true) {
  case number > 0 && number < 10:
    result = "Number is between 0 and 10";
    break;
  case number > 10 && number < 20:
    result = "Number is between 10 and 20";
    break;
  default:
    result = "Number is not in the specified range";
}

console.log(result);

In this example, the output will be "Number is between 0 and 10" because the variable number has a value of 5 and is within the range from 0 to 10.