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ActionScript Basics

1. Comments

• ActionScript supports two kinds of comments:
  C++ Style:     // This is a comment

  C Style:       /* This is a
                 multiline comment. */

2. Primitive Datatypes

• ActionScript supports three primitive datatypes:

  Datatype	Examples
  Boolean	true or false
  Number	3542.433, 0, -143.54, 0xFFFF00
  String	"hello", 'abc', " " (space), "" (empty string)

• Strings can be delimited by either single or double quotes.

• These special characters are available when used inside double quote delimited strings:
  

  \n  New Line
  \r  Carriage Return
  \t  Horizontal Tab
  \\  Backslash
  \'  Single Quote
  \"  Double Quote
  

3. Variables

• As in JavaScript, variables need not be declared.

• However, declaring variables is a good practice:
  var n:Number = 34;

  var b:Boolean = true;

  var s:String = "cat";

• A primitive type can also be defined using class notation, for example:
  var n:Number = new Number(34);

  var b:Boolean = new Boolean(true);

  var s:String = new String("cat");

• ActionScript variable names always begin with a letter, dollar sign or underscore.

• The remaining characters of a variable name can be a letter, digit, a dollar sign or underscore.

4. Operators

• Some ActionScript operators:
  +   -   *   /   %

  =  =+   =-   =*   =/   =%

  ++   --

  <   <=   >   >=   ==   !=

  ===   !==

  &&   ||   !

  ? :

  instanceof   typeof

• Here is a table of return types for the typeof operator

  Datatype	Return String
  Boolean	"boolean"
  Number	"number"
  String	"string"
  MovieClip	"movie clip"
  All other types	"object"

5. Arrays

• Array Creation
  // Create array with zero elements.
  var a:Array = new Array( );

  // Create array with three elements.
  var a:Array = new Array(3);

  // Create array by initialization.
  var a:Array = ["dog", "cat", "mouse"];

• Array Modification
  // Modify an array element.
  a[3] = "horse";

• Reading from an Array
  // Obtain a value from an array.
  x = a[3];

• Appending or Inserting into an Array
  // Appending to the end of an array.
  a.push("Gerbil", "Ferret");

  // Prepending to the beginning of an array.
  a.unshift("Gerbil", "Ferret");

  // Inserting into an array.
  // 2 is the starting index.
  // 0 is the number of elements to delete.
  a.splice(2, 0, "Gerbil", "Ferret");

• Converting Arrays To and From Strings
  // Converting an array to a string.
  s = a.join(";");
  s = a.toString( );

  // Splitting a string into an array.
  a = s.split(",");

• Creating New Arrays from Old
  // Concatenate two arrays a and b.
  c = a.concat(b);

  // Extract a subset of an array.
  b = a.slice(2, 5);
  b = a.slice(2);
  b = a.slice(2, -3);
  b = a.slice(-3);

• Sorting an Array
  // Sort array
  c = a.sort( );
  c = a.sort(Array.NUMERIC);
  c = a.sort(Array.DESCENDING);
  c = a.sort(Array.CASEINSENSITIVE);
  c = a.sort(Array.UNIQUE);
  c = a.sort(Array.RETURNINDEXEDARRAY);
  c = a.sort(Array.NUMERIC | Array.DESCENDING | Array.UNIQUE);

• Reversing an Array
  // Reverse array.
  a.reverse( );

6. String Handling Functions

• Here are some examples of ActionScript string handling functions:
  // Concatenate two strings.
  u = s + t;
  u = s.concat(t);
  u += s;
  u = u.concat(s);

  // Get the length of a string.
  len = s.length;

  // Extracting a substring with substr.
  // 3 is the starting index.
  // 6 is the length of the extracted string.
  u = s.substr(3, 6);
  u = s.substr(-4, 6);

  // Extracting a substring with slice.
  // 3 is the starting index.
  // 9 is the ending index.
  u = s.slice(3, 9);
  u = s.slice(3);
  u = s.slice(-4, 9);
  u = s.slice(-9);

  // Change the case of a string.
  u = s.toLowerCase( );
  u = s.toUpperCase( );

7. Casting

• Casting means convert from one datatype to another.

• Here are some casting examples:
  // Casting to a string to a number.
  n = Number(s);
  n = parseInt(s);
  n = parseFloat(s);

  // Casting from a number to a string.
  s = n.toString(s);

  // Casting from a boolean to a number.
  n = b ? 1 : 0;

  // Casting from a boolean to a string.
  s = b ? "true" : "false";

  // Casting from a number to a boolean.
  b = n != 0; // Casting from a string to a boolean.
  b = s == "true";

7. Control Structures

• The control structures of ActionScript are the same as JavaScript:
  if..else, while, for, for each, switch.

• A one line body does not require braces.

• See this document for the Syntax of ActionScript Control Structures.

8. Builtin Functions

• Some builtin functions of the Math class:
  acos   abs   asin   ceil   cos   exp   floor   log   max   min   random   sin   sqrt