Exploring the execution process of JavaScript statements _ javascript skills

This article will introduce you to the JavaScript statement execution process. If you are interested in the JavaScript statement execution process, let's learn it together. The javascript operating principles are summarized as follows:

1. execute javascript code in sequence according to the html Document Stream

The browser parses the Page Structure and information from top to bottom based on the document stream. The javascript code acts as an embedded script as part of the html document, therefore, the execution sequence of javascript code During loading is determined based on the sequence in which the script tag script appears.

If an external. js file is introduced by using the src attribute of script, it will also be executed according to the order in which the statement appears, and the execution process is part of the document loading. The execution will not be extended because it is an external js file.

2. Relationship between pre-compilation and execution sequence

First, read the following code: