Switch

The switch statement evaluates an expression and allows different blocks of code to execute depending on the result of that expression. It contains any number of case clauses marking code to execute based on values returned by the expression, and an optional default statement marking code that executes if none of the case clauses are true.

The code following a matching case clause will execute until it encounters a break statement, a return statement, or the end of the switch block.

This means that if a break is omitted at the end of one case block, subsequent case blocks and/or the default block will be executed regardless of the value of the original expression.

Syntax

switch (expression) {
  case value1:
    // Statements executed when expression = value1
    break;
  case value2:
    // Statements executed when expression = value2
    break;
  case value3:
    // Statements executed when expression = value3
    break;
  default:
  // Statements executed when expression not equal to value1, value2 or value3
}

With break statements omitted:

switch (expression) {
  case value1:
  // Statements executed when expression = value1
  case value2:
  // Statements executed when expression = value2 or value1
  case value3:
  // Statements executed when expression = value3, value2 or value1
  default:
  // Statements always executed
}

Example

Determine whether a rating is a 5, 4, 3, or something else:

switch (rating) {
  case 5:
    console.log('Excellent 👏');
    break;
  case 4:
    console.log('Good 👍');
    break;
  case 3:
    console.log('Fair 👌');
    break;
  default:
    console.log('Poor 👎');
}

• If rating is 5, print "Excellent 👏".
• If rating is 4, print "Good 👍".
• If rating is 3, print "Fair 👌".
• Else, print "Poor 👎".

Codebyte Example

Here, an expression is used to find whether a number is even, odd, or not a number:

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