#Things to consider
- It’s very common to conflate the terms “async” and “parallel,” but they are actually quite different. Remember, async is about the gap between now and later. But parallel is about things being able to occur simultaneously.
- Because of JavaScript’s single-threading, the code inside of
foo() (and bar()) is atomic, which means that once foo() starts running, the entirety of its code will finish before any of the code in bar() can run, or vice versa. This is called run-to-completion behavior.
- The callback function is the async workhorse for JavaScript, and it does its job respectably.
- Are you catching the notion here that our sequential, blocking brain planning behaviors just don’t map well onto callback-oriented async code? That’s the first major deficiency of callbacks: they express asynchrony in code in ways our brains have to fight just to keep in sync with (pun intended!).