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There are many built-in objects and arrays in Javascript. Each object includes numerous methods. You should have seen date and timeout, but here are samples for you:

• The Date object in Javascript includes methods to extract portions of the date (month, year,..)
• Intro to date from Dr. Dailey's site
• Example Using timeout
• Example of Date for IE
• Example of Date for any Browser
• Example timeout and date

The string object has many methods/functions for you to use. Although it is not usually necessary, you can create a String object with the new operator

• var somestring= new String()
  OR
• var otherstring= new String("How is your day going?")
• String examples
• Strings to format dollar amounts

Arrays revisited. Users can declare arrays or use builtin arrays

• var new TryArray(4)
  declares an array named TryArray with 4 elements. These elements are number 0, 1, 2, 3

  Code	Description	Output
  var sandwiches = new Array("turkey", "chicken", "bacon");	Create an array of 3 elements
  document.write (sandwiches[1]);	Display second element
  if (1 in sandwiches)	Check for second element
  document.write ("<br>there");	found it

• Javascript includes associative arrays also where we can use indices other than numbers. Specifically, strings.
  

  Code	Description	Output
  var names = new Array(3);	Create an array of 3 elements
  names["first"] = "Sue"	set element named first to Sue
  names["second"] = "Dan"	set element named second to Dan
  names["third"] = "Joe"	set element named third to Joe
  document.write (names["first"]);	display element named "first"

  
  
• There are many built-in arrays. For example there is a form array
• Other built-in arrays include all, href, and image
• You can use the getElementByID for accessing form elements

To create 2D arrays, you need an array where each element of the array is an array (think table where each row of a table is an array)
This can be done via a var statement or via a loop in Javascript.
A 4 x 5 example:

var twoDimArray = [new Array(5), new Array(5), new Array(5), new Array(5)]

var twoDimArray = new Array(4);
for (i=0; i < 4; i++)
  twoDimArray[i]=new Array(5);

1. prompts the user for two integers (no errror checking)
   numRows
   numCols
2. creates a 2D array with the appropriate sizes
3. sets each element of the 2D array to be the product of its rowNum and colNum
4. Debug the code using alerts!