Six. Default arguments parameter default values

　　Example:

　　

 

　　Precautions: The function is declared by default parameter variables, so no need to declare once again, otherwise it will error

　　Examples of errors are as follows:

　　

 

 　　The method of transfer function parameters values:

　　

 

 　　Note that: If you give the second argument passed by value, and that the first parameter to pass undefined, but can not pass null