Can You Use Expressions in JavaScript Switch Case Statements?

Evaluation of Expressions in Switch Case Statements

In JavaScript, switch statements facilitate conditional execution based on a value's equality to predetermined constants. However, what if you wish to leverage dynamic expressions that evaluate at runtime instead?

The code snippet provided attempts to utilize expressions in switch cases:

<code class="javascript">function reward(amount) {
    var $reward = $("#reward");
    switch (amount) {
        case (amount >= 7500 && amount < 10000):
            $reward.text("Play Station 3");
            break;
        case (amount >= 10000 && amount < 15000):
            $reward.text("XBOX 360");
            break;
        case (amount >= 15000):
            $reward.text("iMac");
            break;
        default:
            $reward.text("No reward");
            break;
    }
}</code>

Unfortunately, this approach does not work as expected. The reason lies in the nature of the switch statement. Each case expression returns a boolean value, indicating whether the condition is true or false. In the given code, the expressions evaluate to true or false, not to the desired constant values.

To address this issue, one can employ a trick where the switch statement evaluates to a constant boolean value (true in this case) and uses expressions within case statements to control execution flow:

<code class="javascript">switch (true) {
  case (amount >= 7500 && amount < 10000):
    // Code
    break;
  case (amount >= 10000 && amount < 15000):
    // Code
    break;
  // etc.
}</code>

This workaround allows for the evaluation of expressions within switch cases, although it introduces some potential drawbacks. Firstly, it requires constant evaluation to true, which may be unnecessary or undesirable in some scenarios. Secondly, the code becomes less concise and potentially more confusing.

An alternative approach is to utilize if-else statements, which provide a more straightforward way of evaluating dynamic expressions and executing corresponding code blocks. The choice between using a workarounded switch statement or if-else statements depends on the specific requirements of the application.

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