In JavaScript, a switch statement is a control flow statement that evaluates an expression and executes code based on matching cases. It provides a more concise and readable way to handle multiple possible conditions compared to nested if...else statements.

Syntax:

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;
  // more cases can be added as needed
  default:
    // code block to be executed if expression does not match any case
}

Parameters:

• expression: The expression whose value is compared against each case.
• value1, value2, etc.: The possible values that expression may match.
• case and break: Each case represents a possible value of the expression. When a case is matched, the associated code block is executed. The break statement is used to exit the switch statement and prevent fall-through to subsequent cases.
• default: An optional default case that is executed if expression does not match any of the specified cases.

Example: Here, the switch statement evaluates the value of the day variable. Depending on the value of day, the corresponding case is matched, and the associated code block is executed. If none of the cases match, the default case is executed. In this case, it day is "Monday", the message “Today is Monday.” will be logged to the console.

Today is Monday.