Recipe 22.1. Calling JavaScript Functions

Problem

You want to call a JavaScript function from ActionScript.

Solution

Use ExternalInterface.call( ).

Discussion

Use the ExternalInterface.call( ) method to make synchronous calls to JavaScript functions from ActionScript. The call( ) method requires at least one parameter as a string specifying the name of the function to call:

ExternalInterface.call("changeTitle");

The function must be defined in the HTML page with the same name:

<script language="JavaScript">
    function changeTitle(title) {
        if(title == undefined) {
            title = "New Title";
        }
        window.title = title;
    }
</script>

If the JavaScript function accepts parameters, you can pass values to it by adding additional parameters when calling the call( ) method. For example, the following passes a value to the changeTitle( ) function:

ExternalInterface.call("changeTitle", "ActionScript 3.0 Cookbook");

Since call( ) is synchronous, any values returned by the JavaScript function are immediately returned to ActionScript. That means you can assign the return value from a call to a variable. The following ActionScript illustrates how that can work:

var title:String = ExternalInterface.call("getTitle");

The JavaScript function for the preceding ActionScript call might look like:

<script language="JavaScript">
    function getTitle(  ) {
        return window.title;
    }
</script>

ExternalInterface works for the following browsers:

Internet Explorer 5.0+ (Windows)
Netscape 8.0+ (Windows and Mac OS X)
Mozilla 1.7.5+ (Windows and Mac OS X)
Firefox 1.0+ (Windows and Mac OS X)
Safari 1.3+ (Mac OS X)

If you need to support a browser that ExternalInterface does not work with, you can still make calls to JavaScript functions. However, you must then use the flash.net.navigateToURL( ) function.

The navigateToURL( ) function is asynchronous, meaning it does not return a value. To call a JavaScript function using navigateToURL( ) you must use a flash.net URLRequest object that has a value using the javascript protocol. The following is an example that calls the JavaScript alert( ) function:

var request:URLRequest = new URLRequest("javascript:alert('example');");
navigateToURL(request);