jangaroo-runtime.2.0.19.source-code.undefined.as Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jangaroo-runtime
There is a newer version: 4.1.8
/**
 * API and documentation by Adobe?.
 * Licensed under http://creativecommons.org/licenses/by-nc-sa/3.0/
 */
package {

/**
 * A special value that applies to untyped variables that have not been initialized or dynamic object properties that are not initialized. In ActionScript 3.0, only variables that are untyped can hold the value undefined, which is not true in ActionScript 1.0 and ActionScript 2.0. For example, both of the following variables are undefined because they are untyped and unitialized:
 * 
 * var foo;
 * var bar:*;
 * The undefined value also applies to uninitialized or undefined properties of dynamic objects. For example, if an object is an instance of the Object class, the value of any dynamically added property is undefined until a value is assigned to that property.
 * Results vary when undefined is used with various functions:
 * 
 * The value returned by String(undefined) is "undefined" (undefined is converted to a string).
 * The value returned by Number(undefined) is NaN.
 * The value returned by int(undefined) and uint(undefined) is 0.
 * The value returned by Object(undefined) is a new Object instance.
 * When the value undefined is assigned to a typed variable, the value is converted to the default value of the data type.
 * Do not confuse undefined with null. When null and undefined are compared with the equality (==) operator, they compare as equal. However, when null and undefined are compared with the strict equality (===) operator, they compare as not equal.
 * @see http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/statements.html#null null
 *
 * @example In the following example, an untyped variable, myVar is declared but not initialized. The value of myVar is undefined because the variable is untyped. This is true whether the variable has no type annotation or uses the special (*) untyped annotation (var myVar:*;).
 *  * // trace value of untyped and uninitialized variable
 * var myVar;
 * trace(myVar); // undefined
 * 
 * The same rule applies to uninitialized properties of a dynamic object. For example, given an instance, obj, of the dynamic class A, the value of obj.propName, which is an uninitialized property of the obj instance, is undefined.
 *  * dynamic class A {}
 * var obj:A = new A()
 *
 * // trace undefined property of obj
 * trace(obj.propName); // undefined
 * 
 */
[Native]
public const undefined: * = {}['']; // prevent compiler warning

}