Arrays in JavaScript

Arrays are used to store numbered pieces of data. Each piece of data is called an element, and the number assigned to is is called its index.

JavaScript arrays are very similar to conventional arrays in other programming languages, but there are some differences:

• An element of an array can be of any type (character string, integer, Boolean, another array)
• Different elements of the same array may be of different types
• The first element of an array is at index 0
• JS arrays can be sparse -- i.e. they can contain non-contiguous elements
• JavaScript arrays are objects so they have properties like length, and built-in methods like join, reverse and sort

Defining arrays

• Arrays can be created like you create objects
  • myArray = new Object()
  • myArray[0] = 1
  • myArray[1] = 2 ...

• You can create arrays with a constructor
• a = new EmptyArray(32)
• a = new Array()
• anotherArray = new Array(16)

• Define and initialize arrays at once
• a = new Array(1, 2, 3, "HTML", "MSIE")

Using array elements

• Reading and writing
  • value = a[0]
  • a[1] = "Dynamic HTML"
  • i = 2; a[i] = "Macromedia Dreamweaver"
  • a[i + 1] = "Allaire HomeSite 4.5"
  • a [10] = a[1]
  • myTools[visual] = "Adobe GoLive"
  • myTools[html] = "Lightning HTML Editor"
  • myTools[email] = "Qualcomm Eudora"
  • myTools[graphics] = "Macromedia Fireworks"

• Adding new elements
  • a[0] = 0
  • a[1] = 23
  • a[1000] = [-1]

• Multi-demensional arrays - array of arrays
  • myTable[state][city] = "The Big Apple"

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