TypeScript Switch Statement: Conditional Control Flow

Learn how to use TypeScript's switch statement for efficient conditional logic, handling multiple cases, and default behavior. Discover best practices and examples.

Switch Statement

The TypeScript switch statement is a powerful control flow structure that allows you to execute different code blocks based on the value of an expression. It's often used as an alternative to multiple if-else statements when you have multiple possible values to check.

Syntax:

Syntax

switch (expression) {
  case value1:
    // Code to execute if expression equals value1
    break;
  case value2:
    // Code to execute if expression equals value2
    break;   

  // ... more cases
  default:
    // Code to execute if no cases match
}

How the Switch Statement Works

  • The switch keyword is followed by an expression enclosed in parentheses.
  • The expression's value is compared to each case label.
  • If a match is found, the corresponding code block is executed.
  • The break statement is essential to prevent execution of subsequent case blocks.
  • If no match is found, the default block (optional) is executed.

Example: Day of the Week

Syntax

let day = new Date().getDay(); // Get the day of the week (0-6)

switch (day) {
  case 0:
    console.log("Sunday");
    break;
  case 1:
    console.log("Monday");
    break;
  case 2:
    console.log("Tuesday");
    break;
  case 3:
    console.log("Wednesday");
    break;
  case 4:
    console.log("Thursday");
    break;
  case 5:
    console.log("Friday");
    break;
  case 6:
    console.log("Saturday");
    break;
  default:
    console.log("Invalid day");
}
Output

Sunday

Important Considerations

  • The expression in the switch statement can be of any data type, but the values in case labels must match the type of the expression.
  • The break statement is crucial to prevent "fallthrough" to the next case block.
  • The default case is optional but recommended for handling unexpected values.
  • You can combine multiple case labels with the same code block if they should produce the same result.

Best Practices

  • Use switch statements when you have multiple discrete values to check.
  • Consider using if-else statements for more complex conditional logic or when ranges of values need to be tested.
  • Always include a default case to handle unexpected values gracefully.
  • Format your switch statements consistently for readability.

By understanding and effectively using TypeScript's switch statement, you can improve the structure and efficiency of your conditional logic.