When is JavaScript synchronous?

Question

I have been under the impression for that JavaScript was always asynchronous. However, I have learned that there are situations where it is not (ie DOM manipulations). Is

Answer 1

JavaScript is single-threaded, and all the time you work on a normal synchronous code-flow execution.

Good examples of the asynchronous behavior that JavaScript can have are events (user interaction, Ajax request results, etc) and timers, basically actions that might happen at any time.

I would recommend you to give a look to the following article:

• How JavaScript Timers Work

That article will help you to understand the single-threaded nature of JavaScript and how timers work internally and how asynchronous JavaScript execution works.