Determining the Size of an Array
All
arrays come with a built-in
property named length
, which indicates the current
number of elements (including empty elements). To access an
array’s length
property, we use the dot
operator, like so:
arrayName
.length
An array’s length
property tells us how many
elements are in the array. Here are a few examples:
myList = [34, 45, 57]; trace(myList.length); // Displays: 3 myWords = ["this", "that", "the other"]; trace(myWords.length); // Displays: 3, the number of elements, // not the number of words or characters frameLabels = new Array(24); // Note the single numeric argument // used with the Array( ) constructor trace(frameLabels.length); // Displays: 24
The length
of an array is always one greater than
the index of its last element. For example, an array with elements at
indexes 0, 1, and 2 has a length of 3. And an array with elements at
indexes 0, 1, 2, and 50 has a length of 51. 51? Yes, 51. Even though
indexes 3 through 49 are empty, they still contribute to the length
of the array. The last element of an array is always
myArray
[
myArray
.length
- 1]
, because index numbers begin at 0, not 1.
If we add and remove elements, the array’s
length
property is updated to reflect our changes.
In fact, we can even set the length
property to
add or remove elements at the end of an array.
What is an array’s length
property good for,
you ask? Using an array’s length
property, we can create a loop that accesses all the elements of an array as we saw in ...
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