JS Errors Silent
Some mistakes produce a wrong value without throwing. Use an explicit check when missing data is not acceptable.
Where to run this
This example uses the JavaScript console playground. Select Run to execute it; the example does not run on this lesson page.
A practical example
const session = {};
if (!Object.hasOwn(session, "places")) {
console.log("The place count is missing.");
}
What happens
The missing field is reported instead of being used in a calculation.