A `?` property is a drawer that might be empty: look before you use it

An optional property may be absent from the object entirely. Reading it yields the property's type plus undefined, so you cannot assign it to a variable of the plain type until you have handled the missing case. If a field must always exist, leave off the ?.

Read it once, then a question tests whether the trick stuck.

A ? property is a drawer that might be empty: look before you use it

A `?` property is a drawer that might be empty: look before you use it