Understanding the ActionScript Language > About built-in objects > Using a built-in object |  |

Using a built-in object

Some built-in Flash objects are top-level objects; you can use the methods and properties of a top-level object without creating a new instance of the object. For example, to use the methods and properties of the top-level Math object, you use the name of the built-in object followed by the method or property, as in the following:

    area = Math.PI * radius * radius;

Other built-in objects, like the Date object, require you to create a new instance of the object to use its methods and properties. You use the `new` operator with a constructor function to create an object. (A constructor function is a function that creates a new instance of an object.) The ActionScript built-in objects are prewritten constructor functions. When you create a new instance of a built-in object, all the properties and methods of that object are copied into the instance. This is similar to dragging a movie clip from the library to the Stage. For example, the following statement creates a new Date object called `currentDate` and then calls the `getMinutes` method:

    currentDate = new Date();
    currentMinute = currentDate.getMinutes();

In the following code, the object `c` is created from the constructor `Color`:

    c = new Color(this);

Each object that requires a constructor function has a corresponding `new` element in its folder in the Actions panel—for example, `new Color`, `new Date`, `new String`, and so on.

You can also use the object initializer operator (`{}`) to create an object of the generic type Object.

To create an object with the `new` operator in normal mode:

1 | Choose Window > Actions to open the Actions panel if it isn't already open.
2 | In the Actions toolbox (at the left of the panel), click the Actions folder to open it, then open the Variables folder.
3 | Double-click the `set variable` action.``
4 | Enter an identifier in the Variable box; this is the name of the new object.
5 | Click in the Value box to place the insertion point. Then browse in the Actions toolbox to the object you want to create, and double-click `new Date`, `new Color`, and so on.
6 | Select the Expression option next to the Value box.
| If you don't select the Expression option, the entire value will be a string literal.

To use the object initializer operator (`{}`) in normal mode:

1 | Choose Window > Actions to open the Actions panel if it isn't already open.
2 | In the Actions toolbox, click the Actions folder to open it. Click the Variables folder to open it.
3 | Double-click the `set variable` action.``
4 | Enter an identifier in the Variable box; this is the name of the new object.
5 | Select the Expression option next to the Value box.
6 | In the Value box, enter the property name and value pairs separated by a colon inside the object initializer operator (`{}`).

For example, in this statement the property names are `radius` and `area` and their values are 5 and the value of an expression:

    myRadius = 5;
    myCircle = {radius: myRadius, area:(Math.PI * myRadius * myRadius)};

The parentheses cause the expression inside them to evaluate. The returned value is assigned to the variable `area`.

You can also nest array and object initializers, as in this statement:

    newObject = {name: "John Smith", projects: ["Flash", "Dreamweaver"]};

For more information on the Actions panel, see Writing Scripts with ActionScript. For detailed information on each object, see its entry in the online ActionScript Dictionary in the Help menu.