Anthony Box7,435 Points
Using slice over filter
When removing by index from the state, why would we use splicing over filtering by index? Is it convention or efficiency? ex. filter((guest, i) => return index == index
The biggest difference is that the filter method creates a new array containing the filtered values, whereas the splice method will edit the existing array directly. These two methods are not interchangeable even though they have similarities. You can write code to change the initial array variable to the new filtered array, which is fine; it's just more verbose than using the splice method.
Steven Parker140,537 Points
I think "slice" and "filter" could be used interchangeably here in modern browsers. The only advantages I can think of to "slice" is that the pattern of "before/after" for removing item(s) is one that would be readily recognized by experienced readers, and support for "slice" has been around since JS1.2, where "filter" was introduced in JS1.6.
Amber's comments relate to "splice" instead of "slice", but they remind me that "splice" might also be a good (and potentially superior) choice here, since the objective is to modify the array anyway.
One thing to keep in mind about the methods shown in course lectures is that they are chosen for clarity and not optimal performance, particularly when an optimal solution might employ a method that has not been introduced in the current course or its prerequisites.