JS call() and apply()

call() and apply()
- Both methods are methods of function objects , You need to call... Through a function object

- When calling a function call() and apply() Will call the function to execute
- Calling call() and apply() You can specify an object as the first parameter
At this point, the object will become the object of the function execution this

- call() Method can pass the arguments after the object in turn
- apply() Method needs to encapsulate the arguments into an array and pass them uniformly

- this The situation of :
1. When called as a function ,this It's always window

2. When called as a method ,this It's the object that calls the method
3. When called as a constructor ,this It's the newly created object

4. Use call and apply Invocation time ,this It's the designated object