Statements and Operators: Chapter 10 - Essential ActionScript

.

15

Multiple uses:

// Access a variable
product.price
// Reference a class
flash.display.Sprite
// Access an XML child element
novel.TITLE

[]

15

Multiple uses:

// Initialize an array
["apple", "orange", "pear"]
// Access fourth element of an array
list[3]
// Access a variable
product["price"]
// Access an XML child element
novel["TITLE"]

( )

15

Multiple uses:

// Force addition before multiplication
(5 + 4) * 2
// Invoke a function
trace( )
// Filter an XMLList
staff.*.(SALARY <= 35000)

@

15

Accesses XML attributes

// Retrieve all attributes of novel
novel.@*

::

15

Separates a qualifier namespace from a name

// Qualify orange with namespace fruit
fruit::orange

..

15

Accesses XML descendants

// Retrieve all descendant elements
// of loan named DIRECTOR
loan..DIRECTOR

{x:y}

15

Creates a new object and initializes its dynamic variables

// Create an object with dynamic variables,
// width and height
{width:30, height:5}

new

15

Creates an instance of a class

// Create TextField instance
new TextField( )

<tag> <tag/>

15

Defines an XML element

// Create an XML element named BOOK
<BOOK>Essential ActionScript 3.0</BOOK>

x++

14

Adds one to x and returns x's former value (postfix increment)

// Increase i by 1, and return i
i++

x--

14

Subtracts one from x and returns x's former value (postfix decrement)

// Decrease i by 1, and return i
i--

++ x

14

Adds one to x and returns x's new value (prefix increment)

// Increase i by 1, and return the result
++i

-- x

14

Subtracts one from x and returns x's new value (prefix decrement)

// Decrease i by 1, and return the result
--i

-

14

Switches the operand's sign (positive becomes negative, and negative becomes positive)

var a:int = 10;
// Assign −10 to b
var b:int = -b;

~

14

Performs a bitwise NOT

// Clear bit 2 of options
options &= ~4;

!

14

Returns the Boolean opposite of its single operand

// If under18's value is not true,
// execute conditional body
if (!under18) {
  trace("You can apply for a credit card")
}

delete

14

Multiple uses:

// Create an array
var genders:Array = ["male","female"]
// Remove the first element's value
delete genders[0];
// Create an object
var o:Object = new Object( );
o.a = 10;
// Remove dynamic instance variable a
delete o.a;
// Remove the <TITLE> element from the XML
// object referenced by novel
delete novel.TITLE;

typeof

14

Returns a simple string description of various types of objects. Used for backwards compatibility with ActionScript 1.0 and ActionScript 2.0 only.

// Retrieve string description of 35's type
typeof 35

void

14

Returns the value undefined

var o:Object = new Object( );
o.a = 10;
// Compare undefined to the value of o.a
if (o.a == void) {
  trace("o.a does not exist, or has no value");
}

*

13

Multiplies two numbers

// Calculate four times six
4 * 6

/

13

Divides left operand by right operand

// Calculate 30 divided by 5
30 / 5

%

13

Returns the remainder (i.e., modulus) that results when the left operand is divided by the right operand

// Calculate remainder of 14 divided by 4
14 % 4

+

12

Multiple uses:

// Calculate 25 plus 10
25 + 10
// Combine "He" and "llo" to form "Hello"
"He" + "llo"
// Combine two XML objects
<JOB>Programmer</JOB> + <AGE>52</AGE>

-

12

Subtracts right operand from left operand

// Subtract 2 from 12
12 - 2

<<

11

Performs a bitwise left shift

// Shift 9 four bits to the left
9 << 4

>>

11

Performs a bitwise signed right shift

// Shift 8 one bit to the right
8 >> 1

>>>

11

Performs a bitwise unsigned right shift

// Shift 8 one bit to the right, filling
// vacated bits with zeros
8 >>> 1

<

10

Checks if the left operand is less than the right operand. Depending upon the evaluation of the operands, returns true or false.

// Check if 5 is less than 6
5 < 6
// Check if "a" has a lower character code point
// than "z"
"a" < "z"

<=

10

Checks if the left operand is less than or equal to the right operand. Depending on the evaluation of the operands, returns true or false.

// Check if 10 is less than or equal to 5
10 <= 5
// Check if "C" has a lower character code point
// than "D", or the same code point as "D"
"C" <= "D"

>

10

Checks if the left operand is greater than the right operand. Depending upon the evaluation of the operands, returns true or false.

// Check if 5 is greater than 6
5 > 6
// Check if "a" has a higher character code point
// than "z"
"a" > "z"

>=

10

Checks if the left operand is greater than or equal to the right operand. Depending on the evaluation of the operands, returns true or false.

// Check if 10 is greater than or equal to 5
10 >= 5
// Check if "C" has a higher character code point
// than "D", or the same code point as "D"
"C" >= "D"

as

Checks if the left operand belongs to the datatype specified by the right operand. If yes, returns the object; otherwise returns null

var d:Date = new Date( )
// Check if d's value belongs to
// the Date datatype
d as Date

is

Checks if the left operand belongs to the datatype specified by the right operand. If yes, returns the true; otherwise returns false.

var a:Array = new Array( )
// Check if a's value belongs to
// the Array datatype
a is Array

in

Checks if an object has a specified public instance variable or public instance method. Depending on the evaluation of the operands, returns true or false.

var d:Date = new Date( )
// Check if d's value has a public variable or
// public method named getMonth
"getMonth" in d

instanceof

10

Checks if the left operand's prototype chain includes the right operand. Depending on the evaluation of the operands, returns true or false.

var s:Sprite = new Sprite( )
// Check if s's value's prototype chain
// includes DisplayObject
s instanceof DisplayObject

==

9

Checks whether two expressions are considered equal (equality). Depending on the evaluation of the operands, returns true or false.

// Check whether the expression "hi" is equal to
// the expression "hello"
"hi" == "hello"

!=

9

Checks whether two expressions are considered not equal (in equality). Depending upon the evaluation of the operands, returns true or false.

// Check whether the expression 3 is not equal to
// the expression 3
3 != 3

===

9

Checks whether two expressions are considered equal without datatype conversion for primitive types (strict equality). Depending on the evaluation of the operands, returns true or false.

// Check whether the expression "3" is equal to
// the expression 3. This code compiles in
// standard mode only.
"3" === 3

!==

9

Checks whether two expressions are considered not equal without datatype conversion for primitive types (strict equality). Depending on the evaluation of the expression, returns true or false.

// Check whether the expression "3" is not equal to
// the expression 3. This code compiles in
// standard mode only.
"3" === 3

&

8

Performs a bitwise AND

// Combine bits of 15 and 4 using bitwise AND
15 & 4

^

7

Performs a bitwise XOR

// Combine bits of 15 and 4 using bitwise XOR
15 ^ 4

|

6

Performs a bitwise OR

// Combine bits of 15 and 4 using bitwise OR
15 | 4

&&

5

Compares two expressions using a logical AND operation. If the left operand is false or converts to false, && returns the left operand; otherwise && returns the right operand.

var validUser:Boolean = true;
var validPassword:Boolean = false;
// Check if both validUser and validPassword
// are true
if (validUser || validPassword) {
  // Do login...
}

||

4

Compares two expressions using a logical OR operation. If the left operand is true or converts to true, || returns the left operand; otherwise || returns the right operand.

var promotionalDay:Boolean = false;
var registeredUser:Boolean = false;
// Check if either promotionalDay or registeredUser
// is true
if (promotionalDay || registeredUser) {
  // Show premium content...
}

?:

3

Performs a simple conditional. If the first operand is true or converts to true, the value of the second operand is evaluated and returned. Otherwise, the value of the third operand is evaluated and returned.

// Invoke one of two methods based on
// whether soundMuted is true
soundMuted ? displayVisualAlarm() : playAudioAlarm( )

=

2

Assigns a value to a variable or array element

// Assign 36 to variable age
var age:int = 36;
// Assign a new array to variable seasons
var seasons:Array = new Array( );
// Assign "winter" to first element of seasons
seasons[0] = "winter";

+=

2

Adds (or concatenates) and reassigns

// Add 10 to n's value
n += 10; // same as n = n + 10;
// Add an exclamation mark to the end of msg
msg += "!"
// Add an <AUTHOR> tag after the first <AUTHOR>
// tag child of novel
novel.AUTHOR[0] += <AUTHOR>Dave Luxton</AUTHOR>;

-=

2

Subtracts and reassigns

// Subtract 10 from n's value
n -= 10; // same as n = n - 10;

*=

2

Multiplies and reassigns

// Multiply n's value by 10
n *= 10; // same as n = n * 10;

/=

2

Divides and reassigns

// Divide n's value by 10
n /= 10; // same as n = n / 10;

%=

2

Performs modulo division and reassigns

// Assign n%4 to n
n %= 4; // same as n = n % 4;

<<=

2

Shifts bits left and reassigns

// Shift n's bits two places to the left
n <<= 2; // same as n = n << 2;

>>=

2

Shifts bits right and reassigns

// Shift n's bits two places to the right
n >>= 2; // same as n = n >> 2;

>>>=

2

Shifts bits right (unsigned) and reassigns

// Shift n's bits two places to the right, filling
// vacated bits with zeros
n >>>= 2; // same as n = n >>> 2;

&=

2

Performs bitwise AND and reassigns

// Combine n's bits with 4 using bitwise AND
n &= 4 // same as n = n & 4;

^=

2

Performs bitwise XOR and reassigns

// Combine n's bits with 4 using bitwise XOR
n ^= 4 // same as n = n ^ 4;

|=

2

Performs bitwise OR and reassigns

// Combine n's bits with 4 using bitwise OR
n |= 4 // same as n = n | 4;

,

1

Evaluates left operand, then right operand

// Initialize and increment two loop counters
for (var i:int = 0, j:int = 10; i < 5; i++, j++) {
  // i counts from 0 through 4
  // j counts from 10 through 14
}