try, catch, finally and throw.
✍️ 3 exercises + code challenge in this lessonWhen something goes wrong, JavaScript throws an error and stops. You can handle errors gracefully:
try { }: code that might fail.catch (error) { }: runs if an error is thrown; error.message describes it.finally { }: always runs, error or not.throw new Error("message"): create your own errors.Built-in error types include ReferenceError, TypeError, SyntaxError and RangeError.
Mastering JavaScript Errors helps you write clean and reliable JavaScript code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.
<pre id="out"></pre>
<script>
const log = (...a) => document.getElementById("out").textContent += a.join(" ") + "\n";
function withdraw(balance, amount) {
if (amount > balance) {
throw new Error("Insufficient balance");
}
return balance - amount;
}
try {
log("New balance:", withdraw(5000, 1500));
log("New balance:", withdraw(5000, 9000));
} catch (error) {
log("Error:", error.message);
} finally {
log("Transaction finished.");
}
try {
undefinedFunction();
} catch (e) {
log(e.name + ":", e.message);
}
</script>Check what you learned in “JavaScript Errors”.
Catch errors thrown in the try block.
try {
riskyCode();
} (error) {
log(error.message);
}
Which block always runs, error or not?
Call JSON.parse on invalid text inside try/catch and log "Invalid JSON" when it fails.
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