6.1. Adding Elements to the Start or End of an Array
Problem
You want to add elements to an existing array.
Solution
Use the push( )
method to append elements to an
array; use the unshift( )
method to insert
elements at the beginning of an array.
Discussion
You can append elements
to an existing array using the
Array.push( )
method, passing it one or more
values to be appended:
myArray = new Array( ); myArray.push("val 1", "val 2");
You can also append a single element using the
array’s length
property as the
index. Because ActionScript array indexes are zero-relative (meaning
that the first index is 0, not 1), the last element is at an index of
Array
.length
- 1.
myArray[myArray.length] = "val 3";
If you try to set an element with an index that does not yet exist,
the array is extended to include the necessary number of elements
automatically (in which case intervening elements are initialized to
undefined
). For example, after executing the
following statements, myArray
contains the
elements ["a”,
“b”,
“c”, undefined
,
undefined
, “f"]:
myArray = ["a", "b", "c"]; myArray[5] = "f";
Appending elements onto an array is common when you want to build an array incrementally or when you want to store the history of a user’s actions for the purpose of implementing a Back button or history feature.
To add elements to the beginning of an array, use the
unshift( )
method, which shifts the existing
elements by one index position, and inserts the new element at index
0:
// Create an array with four elements: ...
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