Switch Statements

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JavaScript Switch Statements

Switch statements in JavaScript are a type of conditional statement that allow you to check the value of an expression and perform different actions based on different cases.

Syntax

The basic syntax of a switch statement is as follows:

switch (expression) {
  case value1:
    // code block to be executed if expression matches value1
    break;
  case value2:
    // code block to be executed if expression matches value2
    break;
  ...
  default:
    // code block to be executed if expression doesn't match any of the cases
}

In a switch statement, the `expression` is evaluated once, and its value is compared with the values of each `case`. If there is a match, the corresponding code block is executed until a `break` statement is encountered or until the end of the switch statement. If no match is found, the code block under the `default` case (if present) will be executed.

Example

Here's an example that demonstrates how to use a switch statement:

let day = new Date().getDay();
  let dayName;
   
  switch (day) {
    case 0:
      dayName = "Sunday";
      break;
    case 1:
      dayName = "Monday";
      break;
    case 2:
      dayName = "Tuesday";
      break;
    case 3:
      dayName = "Wednesday";
      break;
    case 4:
      dayName = "Thursday";
      break;
    case 5:
      dayName = "Friday";
      break;
    case 6:
      dayName = "Saturday";
      break;
    default:
      dayName = "Unknown";
  }
   
  console.log("Today is " + dayName);

In this example, the switch statement checks the value of `day` and assigns the corresponding day name to the variable `dayName`. The `dayName` variable is then printed to the console.

Multiple Cases

You can also have multiple cases that share the same code block. To do this, simply omit the `break` statement for the matching cases: 

let fruit = "apple";
  let season;
   
  switch (fruit) {
    case "apple":
    case "pear":
    case "plum":
      season = "Autumn";
      break;
    case "banana":
    case "mango":
      season = "Summer";
      break;
    case "orange":
    case "grapefruit":
      season = "Winter";
      break;
    default:
      season = "Unknown";
  }
   
  console.log("The season of the fruit is " + season);

In this example, the switch statement checks the value of `fruit` and assigns the corresponding season to the variable `season`. The cases for "apple", "pear", and "plum" share the same code block and will result in the season being set to "Autumn".

Key Takeaways

  • Switch statements allow you to check the value of an expression and perform different actions based on different cases.
  • The `expression` is evaluated once, and its value is compared with the values of each `case`.
  • Each case block should end with a `break` statement to prevent fall-through to the next case.
  • You can have multiple cases that share the same code block by omitting the `break` statement for those cases.
  • The `default` case is optional and is executed if the expression doesn't match any of the cases.

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