Implementation code for synchronous and asynchronous loading of JavaScript files

This article mainly introduces the implementation code of synchronization and asynchronous loading of JavaScript files. It has certain reference and value for learning JavaScript. Those who are interested in JavaScript can learn about this article

Regarding the reference of JS files, although there are currently many frameworks and tools (such as webpack, commonjs, requiresjs, etc.), they have done a good job. But aside from these frameworks, it is still helpful to understand the native loading method. This article briefly describes the synchronous and asynchronous loading methods of some js files.

Synchronous loading

Can be inserted into the html file with the