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This article mainly shows you "JS will block the page?" The content is simple and easy to understand, and the organization is clear. I hope it can help you solve your doubts. Let Xiaobian lead you to study and learn this article "JS will block the page?"

Does JS block pages?

Let's draw a conclusion first.

JS blocks DOM parsing and therefore page loading

This is why we often say that JS files should be placed at the bottom

Since JavaScript is DOM manipulable, if the UI is rendered while modifying these element properties (i.e., JavaScript threads and UI threads are running simultaneously), the element data obtained before and after the rendering thread may be inconsistent.

Therefore, to prevent unexpected rendering results, the browser sets the relationship **"GUI rendering thread and JavaScript engine are mutually exclusive"**.

GUI threads are suspended while the JavaScript engine executes, and GUI updates are stored in a queue until the engine threads are idle and executed immediately.

While the browser is executing JavaScript programs,GUI rendering threads are kept in a queue until the JS program finishes executing.

Therefore, if JS takes too long to execute, this will cause inconsistent rendering of the page, resulting in a feeling of blocked page rendering.

The above is "JS will block the page?" All the contents of this article, thank you for reading! I believe that everyone has a certain understanding, hope to share the content to help everyone, if you still want to learn more knowledge, welcome to pay attention to the industry information channel!

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