8.3.1. Common Array Methods // splice Examples (.splice)

//The general syntax for this method is:
arrayName.splice(index, number of elements to change, item1, item2, ...);

//Inside the parentheses (), only the first argument is required.

/*The splice method modifies one or more elements anywhere in the array. 
Entries can be added, removed, or changed. This method requires 
practice.*/

/*To remove elements from an array, the splice method needs 1 or 2 
arguments.

Given only one argument, splice(index) removes every entry from index
to the end of the array.*/
let arr = ['a', 'b', 'c', 'd', 'e', 'f'];

arr.splice(2);    //Everything from index 2 and beyond is removed.
console.log(arr);

//['a', 'b']


/*With two arguments, splice(index, number of items) starts at index 
and removes the specified number of items from the array.*/
let arr = ['a', 'b', 'c', 'd', 'e', 'f'];

arr.splice(2,3);    //Start at index 2 and remove 3 total entries.
console.log(arr);

arr.splice(1,1);    //Start at index 1 and remove 1 entry.
console.log(arr);

//[ 'a', 'b', 'f' ]
//[ 'a', 'f' ]


/*To add or replace elements in an array, the splice method requires
3 or more arguments.

To add elements, set the number of elements argument to 0 and follow
this with the new items.*/

//Example: 
/*splice(index, 0, new item) starts at index and INSERTS the new items.
Existing elements get shifted further down the array.*/
let arr = ['a', 'b', 'c', 'd', 'e', 'f'];

arr.splice(2,0,'hello');     //Start at index 2, remove 0 entries, and add 'hello'.
console.log(arr);

//[ 'a', 'b', 'hello', 'c', 'd', 'e', 'f' ]


/*To replace elements in an array, the number of elements argument 
must be a positive integer. Follow this with the new items for the 
array.*/

//Example:
/*splice(index, number of items, new items) starts at index and 
REPLACES the number of items with the new ones.*/
let arr = ['a', 'b', 'c', 'd', 'e', 'f'];

arr.splice(2,3,'hello', 9);    //Start at index 2, replace 3 entries with 'hello' and 9.
console.log(arr);

//[ 'a', 'b', 'hello', 9, 'f' ]