The event handler contains a nestedscope called NestedScope. The following variables are defined
该事件处理程序包含一个嵌套范围 NestedScope。
2
An identifier may be defined once in a scope, but can be redefined in nested scopes. The following example will explain some of these points.
一个标识可以在一个作用域中定义一次，但可以在嵌套作用域中重新定义。
3
A local variable is one that is only available for use (that is, you can assign to it, or fetch its value) within the scope in which it is declared, and within nested scopes as well.