promises.js

const post = (userId) => {
	// First check the user exists
	return getUser(userId)
		.then(user => {
			// Ok, so the user aleady exists

			// do some logic

			// Lets try and delete them
			return deleteUser(userId)
				.then(() => {
					// happy days, return a 204
					return 204;
				})
				.catch(() => {
					// Something went wrong, return 500
					return 500;
				});
		})
		.catch(error => {
			// User doesn’t exist, so return a 404
			return 404;
		});
}

/*

So on line 7, if that logic threw an error, it would be caught 
by the catch block returning the 404, which would be misleading.

In that case, I might want to move that `.catch` block to immediately
after the call to getUser. But If I do that, by *returning* the `404`, 
that then gets passed into the `.then` block which calls deleteUser

*/

Why does getUser throw if no matching user is found? Is it your own function or someone else's? Returning 404 on catch seems incorrect since you are not checking what caused the throw.