You define a variable with a single declarationstatement.
可以使用单个声明语句定义变量。
2
Every local variable must appear in a declarationstatement before being used in any other kind of statement.
每个局部变量在用于其他任何类型的语句前必须出现在声明语句中。
3
This means that the value of a local constant is undefined until the constant declarationstatement is reached and that a local variable is undefined until the variable is assigned to in the function.