Chapter 7: Flow Control in Modern JS: Callbacks to Promises to Async/Await
by Craig Buckler
JavaScript is regularly claimed to be asynchronous. What does that mean? How does it affect development? How has the approach changed in recent years?
Consider the following code:
result1 = doSomething1();
result2 = doSomething2(result1);
Most languages process each line synchronously. The first line runs and returns a result. The second line runs once the first has finished regardless of how long it takes.
Single-thread Processing
JavaScript runs on a single processing thread. When executing in a browser tab, everything else stops. This is necessary because changes to the page DOM can’t occur on parallel threads; it would be dangerous to have one thread ...
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