Except for the core directive of the default setting v-model and v-show Vue also allows you to register custom directives

Let’s register a global directive. The v-focus function of this directive is to get focus on the element when the page is loaded

2.16.1. Example 

When loading the page，input Element automatically obtains focus：
    
 We can also use it in an example   directives   option to register local directives, so that instructions can only be used in this instance: 
 
 
 
 
  2.16.2.  Example  
 
 
 
When loading the page，input Element automatically obtains focus：