javascript

Chapter 5: Reference Types
Perhaps the most powerful array method is splice() , which can be used in a variety of ways. The main
purpose of splice() is to insert items into the middle of an array, but there are three distinct ways of
using this method. They are as follows:
Deletion — Any number of items can be deleted from the array by specifying just two
arguments: the position of the first item to delete and the number of items to delete. For
example, splice(0, 2) deletes the first two items.
Insertion — Items can be inserted into a specific position by providing three arguments: the
starting position, 0 (the number of items to delete), and the item to insert. Optionally, you can
specify a fourth, fifth, or any number of other parameters to insert. For example, splice(2, 0,
“ red ” , “ green “ ) inserts the strings “ red ” and “ green ” into the array at position 2.
Replacement — Items can be inserted into a specific position while simultaneously deleting
items if you specify three arguments: the starting position, the number of items to delete, and
any number of items to insert. The number of items to insert doesn ’ t have to match the number
of items to delete. For example, splice(2, 1, “ red ” , “ green “ ) deletes one item at position
2 and then inserts the strings “ red ” and “ green ” into the array at position 2.
The splice() method always returns an array that contains any items that were removed from the array
(or an empty array if no items were removed). These three uses are illustrated in the following code:
var colors = [“red”, “green”, “blue”];
var removed = colors.splice(0,1);
alert(colors); //green,blue
alert(removed); //red - one item array
//remove the first item
removed = colors.splice(1, 0, “yellow”, “orange”); //insert two items at position 1
alert(colors); //green,yellow,orange,blue
alert(removed); //empty array
removed = colors.splice(1, 1, “red”, “purple”);
alert(colors); //green,red,purple,orange,blue
alert(removed); //yellow - one item array
//insert two values, remove one
This example begins with the colors array containing three items. When splice is called the first time, it
simply removes the first item, leaving colors with the items “ green ” and “ blue ” . The second time
splice() is called, it inserts two items at position 1, resulting in colors containing “ green ” ,
“ yellow ” , “ orange ” , and “ blue ” . No items are removed at this point, so an empty array is returned.
The last time splice() is called, it removes one item, beginning in position 1, and inserts “ red ” and
“ purple ” . After all of this code has been executed, the colors array contains “ green ” ,
“ red ” , “ purple ” , “ orange ” , and “ blue ” .
The Date Type
The ECMAScript Date type is based on an early version of java.util.Date from Java. As such, the
Date type stores dates as the number of milliseconds that have passed since midnight on January 1, 1970
UTC (Universal Time Code). Using this data storage format, the Date type can accurately represent
dates 285,616 years before or after January 1, 1970.
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