How to check if an object has a property

Just a quick tip today. When working with object properties, I often checked for truthiness before doing something.

if (data.isRunning) {
	// Do something...
	console.log('Yep!');
}

This will log "Yep!" into the console if data.isRunning is any value other than null, undefined, false, or 0.

But what if you want to run some code as long as the value exists, even if it’s falsy?

For that, you can use the in operator.

if ('isRunning' in data) {
	// Do something...
	console.log('Yep!');
}

Now, "Yep!" will log into the console as long as isRunning is a property of the data object… even if it’s null, undefined, false, or 0.