Closures are essential in asynchronous programming because they enable asynchronous callbacks to retain access to variables from their outer scope, even after the execution of the outer function has completed.
In the above code, when setTimeout is invoked, the delayedLog function completes its execution and is removed from the call stack. However, the callback function inside setTimeout forms a closure over the lexical environment of delayedLog. This closure makes sure that the message variable remains accessible to the callback function even after delayedLog has finished executing. Without closures, the callback function would lose access to the variable message once delayedLog function completes its execution.