JavaScript Fundamentals · Conditions · Lesson 8 of 48
Switch Statements
Concept
Switch Statements
A switch statement is a cleaner way to handle many possible exact-match values for a single variable, instead of writing a long chain of else if statements.
By the end of this lesson
- Explain the core idea behind Switch Statements.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Syntax
switch (expression) {
case value1:
// code
break;
default:
// code
}ExampleRunnable
let day = "Mon";
switch (day) {
case "Mon":
console.log("Start of week");
break;
default:
console.log("Some other day");
}Falling through on purpose
let month = "Feb";
switch (month) {
case "Dec":
case "Jan":
case "Feb":
console.log("Winter");
break;
default:
console.log("Not winter");
}Note: Stacking case labels with no code between them lets several values share the same block.
Good to know
Forgetting break is one of the most common switch bugs — without it, execution 'falls through' into the next case.
Self-check before continuing
Without looking at the example, describe what changes when you modify one input in Switch Statements. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Write a switch statement that logs a greeting in a different language based on a lang variable.
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Console