Events when the user leaves the page and returns to the page (tag switching)

The user leaves the page, but does not close the page.

When onload and onUnload are used at the very beginning, they indicate the events triggered when the page is closed and the page is opened. They are not the events when the user leaves the page to view another page.

Then the test shows that the event that the user leaves the page takes effect is: blur & focus;

The specific test code is as follows:

<! Doctype HTML>  
After running the page, When you switch the tag, it prints a series of data.
This article is only used to describe that The Blur event of the window will be triggered when the user leaves the current page. When the user returns to the current page again, the focus event of the window will be triggered.