Introduction to the three-level linkage function of JavaScript development

Three-level linkage:

Mainly refers to the interrelated changes between controls on the application user interface. These controls include drop-down boxes, text boxes, labels, menus, etc.

For example, use two drop-down boxes to list the names of provinces and cities respectively. When the user selects the name of the province (or autonomous region or municipality) in the list of the first drop-down box, the The city names in the province (or autonomous region, or municipality directly under the Central Government) will be automatically displayed for users to choose.

This function is also often used in daily work and life, such as Taobao. This function will appear when filling in the delivery address.

In the following chapters, we will learn how to implement this function with JS.