Adobe 12040118 - After Effects Standard Guide

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Overview
The Adobe After Effects 6.5 Render Automation & Scripting Guide demonstrates how to take procedural control
of your After Effects projects via scripting. This feature set is available only in Adobe After Effects 6.5 Profes-
sional Edition.
With the use of system-level scripting, you can streamline your render pipeline and avoid a lot of repetitive
pointing and clicking. If you have used expressions or other JavaScript-like techniques for animating, or
worked with system scripting in AppleScript or Visual Basic, you will recognize the power of application
scripting in After Effects. With some practice, and with sufficient experience using the JavaScript language,
you can take control of your graphics pipeline.
If you know nothing about scripting
After Effects 6.5 is a visual tool with a graphical user interface; you are used to interacting with it via interface
elements such as menus, palettes and icons. For the most part, this is the most accessible way to work.
Scripting is designed for situations in which this methodology involves tedious repetition or painstaking
searching and sorting that could be automated. It is also useful for leveraging the power of networked
rendering in situations where Watch Folder is less powerful (and less convenient to set up).
Scripting is designed to help users of After Effects get past these types of obstacles, and it is available even to
users who have no inclination to learn the JavaScript language. If you are this type of user, you can still harness
the power of scripting via third party solutions such as Rush Render Queue, a graphical user interface to set
up distributed renders from any computer on the network without having to set up on individual machines.
You can also leverage the contributions of scripting users who share scripts with other users. Larger studios
may have such users in-house, while other users can visit forums such as those found at www.adobe-
forums.com.
After Effects objects
You may not think of After Effects as a collection of hierarchical objects, but when you make use of render
queue items, compositions, and projects, that is how they appear in scripting. Just as the expressions features
in After Effects give you access to virtually any property of any layer inside any composition of your project
(each of which we refer to as an object), scripting gives you access to the hierarchy of objects within After
Effects and allows you to make changes to these objects.
After Effects scripting is based on ECMAScript (or more specifically, the 3rd Edition of the ECMA-262
Standard). Further documentation on this standard can be found at www.ecma-international.org.
Expressions and motion math
Because scripting can access individual layer properties, and because it utilizes JavaScript, one might assume
that expressions and scripting are one and the same. However, they are two entirely distinct entities. Expres-
sions have no ability to access information from scripts (such as variables and functions), although a script
can be written to create or edit an expression.
The similarity between expressions and scripting is, however, apparent in that they are both drawn from the
same language, ECMA standard JavaScript. Thus, knowing how to utilize one is helpful in understanding the
other.

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Motion math is no longer included in After Effects; its functionality has been superseded by scripting and
expressions. All mathematical and logical operators common to ECMAScript are available in scripting.
For example, with expressions it is possible to simulate the physics of a a bouncing ball by applying mathe-
matical rules to a“ball” layer. But using scripting, you can create a whole user interface that allows a bouncing
ball and shadow layer to be animated using criteria entered by the user.
About this guide
This guide is for users who manage a graphics pipeline (which may include other scriptable applications as
well) and who want to write scripts to add custom capabilities to After Effects.
This functionality is also offered via third-party network rendering management solutions. These products
feature software designed to help manage this process, so it is possible to take advantage of this functionality
without having to perform manual editing of scripts.
Although this guide is intended to provide an understanding of the extensions that have been added to the
ECMAScript/JavaScript language for scripting of After Effects projects, to take full advantage of what is
possible with scripting you will also need an understanding of writing scripts at the system level (for
integration with AppleScript on the Mac and DOS shell scripts on Windows systems) and a background in
how to work with JavaScript.
Much of what scripting can accomplish replicates what can be done via the After Effects user interface, so a
thorough knowledge of the application itself is also essential to understanding how to use this functionality.
Note that JavaScript objects normally referred to as “properties” are consistently called “attributes” in this
guide, to avoid confusion with After Effects’ own definition of a Property (an animatable value of an effect or
transform within an individual layer).
Activating full scripting features
For security reasons, the scripting features that operate outside the After Effects application (such as adding
and deleting files and folders on volumes, or accessing the network) are disabled by default.
To enable these features, choose Preferences > General, and select Allow Scripts to Write Files and Access
Network.
By selecting this box, you enable the following:
•
Writing files
•
Creating folders
•
Setting the current folder
•
Creating a socket
•
Opening a socket
•
Listening to a socket
The JavaScript Debugger is disabled by default so that casual users do not encounter it. When editing or
writing scripts, the JavaScript Debugger can help you diagnose script problems more quickly.
To activate the JavaScript Debugger on the local machine when a script error is encountered, choose Prefer-
ences > General, and select Enable JavaScript Debugger.
Note that the JavaScript Debugger operates only when executing a script, not with expressions, even though
expressions also make use of JavaScript.

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For detailed information on the JavaScript Debugger, see “JavaScript Debugging” on page 15.
Accessing and writing scripts
To create and edit scripts for After Effects, use an external text-editing application that creates files with
Unicode UTF-8 text encoding. Beware of applications such as Microsoft Word that by default add header
information to files (these create line 0 errors in scripts, causing them to fail). A script can reside anywhere,
although to appear in the Scripts menu it must be saved in the Scripts folder within the After Effects appli-
cation folder. For details on writing and editing scripts, see “Writing Scripts” on page 6.
There is no built-in method for recording a series of actions in After Effects into a script, as you can with
Photoshop actions. Scripts are created outside After Effects and then executed within it, or externally via a
command-line or third-party render management software.
Uses of After Effects scripting
One primary use for scripting in After Effects 6.5 is render automation. Anyone charged with managing a
complex rendering pipeline will be interested in this. Render automation can be accomplished either by hand-
coding scripts or via a third-party network rendering solution that supports automated management of
network rendering pipelines.
There are other uses for scripting; it can be a shortcut around tedious tasks that would otherwise involve
repetitious pointing and clicking.
See “Examples” on page 179 for examples of what scripts can do.

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Writing Scripts
When you use Adobe After Effects, you create projects, compositions, and Render Queue items along with all
of the elements that they contain: footage, images, solids, layers, masks, effects, and properties. Each of these
items, in scripting terms, is an object.
The heart of a scriptable application is the object model. In After Effects, the object model is composed of
projects, items, compositions, layers, and Render Queue items. Each object has its own special attributes, and
every object in an After Effects project has its own identity (although not all are accessible to scripting).
You should be familiar with the After Effects object model in order to create scripts. For more resources for
learning scripting, see “More resources to learn scripting” on page 8.
Editing scripts
After Effects 6.5 does not include a script editor. You can use any text editor to create, edit, and save scripts,
but it is recommended that you choose an application that does not automatically add header information
when saving files and that saves with Unicode (UTF-8) encoding.
Windows applications that are useful for editing scripts include EM Editor or the built-in Notepad (be sure to
set Encoding within save options to UTF-8).
Mac OS applications that are useful for editing scripts include BBEdit or the built-in OS X Textedit (be sure
to set the Save type in Preferences to Unicode [UTF-8]).
The .jsx format
After Effects scripts must include the .jsx file extension in order to be properly recognized by the application.
This extension is a variation on the standard “.js” extension used with normal JavaScript files; any UTF-8
encoded text file with this extension will be recognized.
The Scripts menu and Scripts folder
After Effects scripts reside in the Scripts folder, within the same folder as your After Effects 6.5 application file.
Only scripts contained in this Scripts folder are automatically listed in the Scripts menu, although a script file
can reside anywhere.
To run a script that does not appear in the Scripts menu, choose File > Run Script > Choose File, and choose
the script in the Open dialog box. Alternatively, you can send After Effects a script from a command line (on
Windows) or from AppleScript (on Mac OS).
To appear in the Open dialog box, your script must include the proper .jsx file extension.
Shutdown and Startup folders
Within the Scripts folder are two folders called Startup and Shutdown. After Effects runs scripts in these
folders automatically on starting and quitting, respectively.
In the Startup folder you can place scripts that you wish to execute at startup of the application. They are
executed after the application is initialized and all plug-ins are loaded.

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Scripting shares a global environment,so any script executed at startup can define variables and functions that
are available to all scripts. In all cases, variables and functions, once defined by running a script that contains
them, persist in succeeding scripts during a given After Effects session. Once the application is quit, all such
globally defined variables and functions are cleared.
Please note that this persistence of global settings also means that if you are not careful about giving variables
in scripts unique names, you can inadvertently reassign global variables intended to persist throughout a
session.
Properties can also be embedded in existing objects such as the Application object (see “Application object”
on page 26) to extend the application for other scripts.
The Shutdown folder scripts are executed as the application quits. This occurs after the project is closed but
before any other application shutdown occurs.
Sending a script to After Effects from the system
If you are familiar with how to run a script from the command line in Windows or via AppleScript, you can
send a script directly to the open After Effects application, which then runs automatically.
How to include After Effects scripting in a command line (Windows)
Following are examples of DOS shell scripts that will send an After Effects script to the application without
using the After Effects user interface to execute the script.
In the first example, you would copy and paste your After Effects script directly into the command line script
and then run it, as follows (your script text would appear in quotation marks following the afterfx.exe -s
command):
afterfx.exe –s “alert (“You just sent an alert to After Effects”)”
Alternatively, you could specify the location of the .jsx file to be executed, as follows:
afterfx.exe –r c:\myDocuments\Scripts\yourAEScriptHere.jsx
How to include After Effects scripting in an AppleScript (Mac OS)
Following are three examples of AppleScripts that will send an existing .jsx file containing an After Effects
script to the application without using the After Effects user interface to execute the script.
In the first example, you copy your After Effects script directly into the AppleScript and then run it, as follows
(your script text would appear in quotation marks following the DoScript command):
tell application “Adobe After Effects 6.5”
DoScript “alert (\”You just sent an alert to After Effects\”)”
end tell
Alternatively, you could display a dialog box asking for the location of the .jsx file to be executed, as follows:
set thefile to choose file
tell application “Adobe After Effects 6.5”
DoScript thefile
end tell

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Finally, this script is perhaps most useful when you are working directly on editing a .jsx script and want to
send it to After Effects for testing or to run. To use it effectively you must enter the application that contains
the open .jsx file (in this example it is TextEdit); if you do not know the proper name of the application, type
in your best guess to replace “TextEdit” and AppleScript prompts you to locate it.
Simply highlight the script text that you want to run, and then activate this AppleScript:
(*
This script sends the current selection to After Effects as a script.
*)
tell application “TextEdit”
set the_script to selection as text
end tell
tell application "Adobe After Effects 6.5"
activate
DoScript the_script
end tell
For more information on using AppleScript, check out Matt Neuberg’s AppleScript: the Definitive Guide
(O’Reilly & Associates) or Sal Soghoian’s
AppleScript 1-2-3 (Peachpit Press).
Testing and troubleshooting
Any After Effects script that contains an error preventing it from being completed generates an error message
from the application. This error message includes information about the nature of the error and the line of
the script on which it occurred.
Additionally, After Effects includes a JavaScript debugger. For more information on activating and using the
debugger, see “JavaScript Debugging” on page 15.
More resources to learn scripting
Many resources exist for learning more about scripting that uses the ECMA standard.
The After Effects scripting engine supports the 3rd Edition of the ECMA-262 Standard, including its
notational and lexical conventions, types, objects, expressions and statements.
For a complete listing of the keywords and operators included with ECMAScript, please refer to Ecma-
262.pdf, available at www.ecma-international.org/publications/standards/ECMA-262.HTM.
Books that deal with JavaScript 1.2 are also useful for understanding how scripting works in After Effects. One
book that is something of a standard for JavaScript users is
JavaScript, The Definitive Guide (O’Reilly) by David
Flanagan. Another very readable source is
JavaScript: A Beginner’s Guide (Osborne) by John Pollock. Both of
these texts contain information that pertains only to extensions of JavaScript for Internet browsers; however,
they also contain thorough descriptions of scripting fundamentals.
There are also books for using AppleScript and creating Windows command line scripts, each of which can be
used to send scripts to After Effects.

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Keywords and statement syntax
Although it is not possible to provide an exhaustive resource describing usage of JavaScript, the following
tables provide an overview of keywords, statements, operators, precedence and associativity.
The following table lists and describes all keywords and statements recognized by the After Effects scripting
engine.
Table 1 Keywords and Statement Syntax
Operators
The following tables list and describe all operators recognized by the After Effects scripting engine and show
the precedence and associativity for all operators.
Table 2 Description of Operators
Keyword/Statement Description
break
Standard JavaScript; exit the currently executing loop.
continue
Standard JavaScript; cease execution of the current loop iteration.
case
label used in a switch statement
default
label used in a switch statement when a case label is not found
do - while
Standard JavaScript construct. Similar to the while loop,except loop condition evaluation occurs
at the end of the loop.
false
Literal representing boolean false.
for
Standard JavaScript loop construct.
for - in
Standard JavaScript construct. Provides a way to easily loop through the properties of an object.
function
Used to define a function.
if/if - else
Standard JavaScript conditional constructs.
new
Standard JavaScript constructor statement.
null
Assigned to a variable, array element,or object property to indicate that it does not contain a legal
value.
return
Standard JavaScript way of returning a value from a function or exiting a function.
switch
Standard JavaScript way of evaluating an expression and attempting to match the expression's
value to a
case
label.
this
Standard JavaScript method of indicating the current object.
true
Literal representing boolean true.
undefined
Indicates that the variable, array element, or object property has not yet been assigned a value.
var
Standard JavaScript syntax used to declare a local variable.
while
Standard JavaScript construct. Similar to the
do - while
loop,except loop condition evaluation
occurs at the beginning of the loop.
with
Standard JavaScript construct used to specify an object to use in ensuing statements.
Operators Description
new
Allocate object.

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delete
Deallocate object.
typeof
Returns data type.
void
Returns undefined value.
.
Structure member.
[]
Array element.
()
Function call.
++
Pre- or post-increment.
--
Pre- or post-decrement.
-
Unary negation or subtraction.
~
Bitwise NOT.
!
Logical NOT.
*
Multiply.
/
Divide.
%
Modulo division.
+
Add.
<<
Bitwise left shift.
>>
Bitwise right shift.
>>>
Unsigned bitwise right shift.
<
Less than.
<=
Less than or equal.
>
Greater than.
>=
Greater than or equal.
==
Equal.
!=
Not equal.
&
Bitwise AND.
^
Bitwise XOR.
|
Bitwise OR.
&&
Logical AND.
||
Logical OR.
?:
Conditional (ternary).
=
Assignment.
+=
Assignment with add operation.
-=
Assignment with subtract operation.
*=
Assignment with multiply operation.
Operators Description

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Table 3 Operator Precedence
Render automation with aerender
One primary use for scripting in After Effects 6.5 is render automation. Anyone charged with managing a
complex rendering pipeline will be interested in this. Render automation can be accomplished either by hand-
coding scripts or via a third-party network rendering solution that supports automated management of
network rendering pipelines.
Note: There are other uses for scripting; it can be a shortcut around tedious tasks that would otherwise involve
repetitious pointing and clicking. See “Examples” on page 179 for examples of what scripts can do.
/=
Assignment with divide operation.
%=
Assignment with modulo operation.
<<=
Assignment with bitwise left shift operation.
>>=
Assignment with bitwise right shift operation.
>>>=
Assignment with bitwise right shift unsigned operation.
&=
Assignment with bitwise AND operation.
^=
Assignment with bitwise XOR operation.
|=
Assignment with bitwise OR operation.
,
Multiple evaluation.
Operators (Listed from highest precedence —top row—to lowest) Associativity
[], (), .
left to right
new, delete, -(unary negation), ~, !, typeof, void,++, -- right to left
*, /, % left to right
+, -(subtraction) left to right
<<, >>, >>> left to right
<, <=, >, >= left to right
==, != left to right
&left to right
^left to right
|left to right
&& left to right
|| left to right
?: right to left
=, /=, %=, <<=, >>=, >>>=, &=, ^=, |=, +=, -=, *= right to left
,left to right
Operators Description

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Usage
The command-line application aerender renders After Effects compositions. The render may be performed
either by an already running instance of After Effects or by a newly invoked instance. By default, aerender will
invoke a new instance of After Effects, even if one is already running. To change this, see the "-reuse" flag in
the following “Arguments” below.
Arguments
From the command line aerender takes a series of optional arguments that are added following the executable
command (i.e. aerender.exe). Some are single flags, like "-reuse". Some come in flag-argument pairs, like "-
project project_path". And one comes in a triplet, -mem_usage image_cache_percent max_mem_percent.
With 0 arguments, or with any argument equaling "-help", aerender prints a usage message with the infor-
mation contained in this section.
Argument Usage
-help print usage message
-reuse Use this flag if you want to try and reuse an already running instance
of After Effects to perform the render. By default, aerender launches
a new instance of After Effects, even if one is already running. But,
if After Effects is already running, and the -reuse flag is provided,
aerender asks the already running instance of After Effects to
perform the render. Whenever aerender launches a new instance of
After Effects, it tells After Effects to quit when rendering is
completed; otherwise, it doesn’t quit After Effects. Also, the prefer-
ences are written to file upon quitting when the -reuse flag is
specified; otherwise it isn’t written.
-project project_path where project_path is a file path or URI specifying a project file to
open. If none is provided, aerender will work with the currently
open project. If no project is open and no project is provided, an
error will result.
-comp comp_name where comp_name specifies a comp to be rendered.
If the comp is in the render queue already, and in a queueable state,
then (only) the first queueable instance of that comp on the render-
queue is rendered.
If the comp is in the project but not in the render queue, then it is
added to the render queue and rendered.
If no -comp argument is provided, aerender renders the entire
render queue as is. In this case (no -comp), the only other
arguments used are -project, -log, -v, -mem_usage, and -close;
the -RStemplate, -OMtemplate, -output, -s, -e, and arguments
are ignored.

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-RStemplate
render_settings_template
where render_settings_template is the name of a template to apply
to the render queue item.
If the template does not exist, it is an error. Default is to use the
render template already defined for the item.
-OMtemplate
output_module_template
where output_module_template is the name of a template to apply
to the output module. If the template does not exist, it is an error.
Default is to use the template already defined for the output
module.
-output output_path where output_path is a file path or URI specifying the destination
render file. Default is the path already in the project file.
-log logfile_path where logfile_path is a file path or URI specifying the location of
the log file. Default is stdout.
-s start_frame where start_frame is the first frame to render. Default is the start
frame in the file.
-e end_frame where end_frame is the last frame to render.Note,this is "inclusive;"
the final frame is rendered. Default is the end frame in the file.
-i increment where increment is the number of frames to advance before
rendering a new frame. A value of 1 (the default) results in a normal
rendering of all frames. Higher increments will repeat the same
(frame increment-1) times and then render a new one, starting the
cycle again. Higher values result in faster renders but choppier
motion. Default is 1.
-mem_usage
image_cache_percent
max_mem_percent
where image_cache_percent specifies the maximum percent of
memory used to cache already rendered images/footage, and
max_mem_percent specifies the total percent of memory that can
be used by After Effects.
-v verbose_flag where verbose_flag specifies the type of messages reported.
Possible values are ERRORS (prints only fatal and problem errors)
or ERRORS_AND_PROGRESS (prints progress of rendering as
well). Default value is ERRORS_AND_PROGRESS.
-close close_flag where close_flag specifies whether or not toclose the project when
done rendering, and whether or not to save changes.
If close_flag is DO_NOT_SAVE_CHANGES, the project is closed
without saving changes.
If close_flag is SAVE_CHANGES, project is closed and changes are
saved. If close_flag is DO_NOT_CLOSE the project is left open; but
the project is left open only if using an already-running instance of
After Effects, since new invocations of After Effects must always
close and quit when done. Default value is
DO_NOT_SAVE_CHANGES.
Argument Usage

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Examples
To render just Comp 1 to a specified file, enter:
aerender -project c:\projects\proj1.aep -comp "Comp 1" -output c:\output\proj1\proj1.avi
To render everything in the render queue as is in the project file, enter:
aerender -project c:\projects\proj1.aep
To render frames 1-10 using multi-machine render, enter:
aerender -project c:\projects\proj1.aep -comp "Comp 1" -s 1 -e 10
-RStemplate "Multi-Machine Settings"
-OMtemplate "Multi-Machine Sequence"
-output c:\output\proj1\frames[####].psd
-sound sound_flag where sound_flag specifies whether or not to play a sound when
rendering is complete. Possible values are ON or OFF. Default value
is OFF.
-version Displays the version number of aerender to the console. Does not
render.
Argument Usage

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Help JavaScriptDebugging
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JavaScript Debugging
This section describes the JavaScript Debugger, which appears when the Enable JavaScript Debugger
preference is selected in General Preferences (it is deselected by default) and there is an error when executing
a script.
JavaScript Debugger window
A. Stack trace view B. Resume C. Pause D. Stop E. Step over F. Step into
G. Step out H. Breakpoints display I. Command line J. Debug output view
K. JavaScript source view
The current stack trace appears in the upper-left pane of the JavaScript Debugger window. This Stack Trace
view displays the calling hierarchy at the time of the breakpoint. Double-clicking a line in this view changes
the current scope, enabling you to inspect and modify scope-specific data.
All debugging output appears in the upper-right pane of the JavaScript Debugger window. Specifically, output
from the print method of the $object appears in this Debug Output view.
The currently executing JavaScript source appears in the lower pane of the JavaScript Debugger window.
Double-clicking a line in this JavaScript Source view sets or clears an unconditional breakpoint on that line.
That is, if a breakpoint is in effect for that line, double-clicking it clears the breakpoint, and vice-versa. The
line number display on the left part displays a red dot for all lines with a breakpoint.
I
J
K
BACDEFGH

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If Enable JavaScript Debugger is deselected in General Preferences, you see an error message but not the
JavaScript Debugger itself. This is the typical setup used in situations in which professional roles are divided
between those writing and administering scripts (technical directors, system administrators, and so on) and
those using them (the artist or animators). If you are writing and debugging your own scripts, you will want
to enable the JavaScript Debugger.
Controlling code execution in the JavaScript Debugger
This section describes the buttons that control the execution of code when the JavaScript Debugger window
is active. Most of these buttons also provide a keyboard shortcut.
Resume
Ctrl+R (Windows)
Command+R (Mac OS)
Resume execution of the script with the JavaScript Debugger window open. When the script terminates, the application closes the Jav-
aScript Debugger window automatically. Closing the window manually also causes script execution to resume. This button is enabled
when script execution is paused or stopped.
Pause
Ctrl+P (Windows)
Command+P (Mac OS)
Halt the currently executing script temporarily and reactivate the JavaScript Debugger. This button is enabled when a script is running.
,,Ray, funnyy wrapping on this line . . . -cj>>
Stop
Ctrl+K (Windows)
Command+K (Mac OS)
Stop execution of the script and generate a runtime error. This button is enabled when a script is running.
Step Over
Ctrl+S (Windows)
Command+S (Mac OS)
Halt after executing a single JavaScript statement in the script; if the statement calls a JavaScript function, execute the function in its
entirety before stopping.
Step Into
Ctrl+T (Windows)
Command+T (Mac OS)
Halt after executing a single JavaScript statement in the script or after executing a single statement in any JavaScript function that the
script calls.

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Step Out
Ctrl+U (Windows)
Command+U (Mac OS)
When the JavaScript Debugger is paused within the body of a JavaScript function, resume script execution until the function returns.
When the JavaScript Debugger is paused outside the body of a function, resume script execution until the script terminates.
Script Breakpoints Display
Display the Script Breakpoints window.
Using the JavaScript command line entry field
You can use the JavaScript Debugger’s command line entry field to enter and execute JavaScript code interac-
tively within a specified stack scope. Commands entered in this field execute with a time-out of one second. If
a command takes longer than one second to execute, the script terminates and generates a time-out error.
Command line entry field
Enter in this field a JavaScript statement to execute within the stack scope of the line highlighted in the Stack
Trace view. When you’ve finished entering the JavaScript expression, you can execute it by clicking the
Command Line Entry button or pressing the Enter key. Click the button next to the field, or press Enter to
execute the JavaScript code in the command line entry field. The application executes the contents of the
command line entry field within the stack scope of the line highlighted in the Stack Trace view.
The command line entry field accepts any JavaScript code, making it very convenient to use for inspecting or
changing the contents of variables.
Note: To list the contents of an object as if it were JavaScript source code, enter the object.toSource() command.
Setting breakpoints
You can set breakpoints in the JavaScript Debugger itself, by calling methods of the $ object, or by defining
them in your JavaScript code.
Setting breakpoints in the JavaScript Debugger
When the JavaScript Debugger window is active, you can double-click a line in the JavaScript Source view to
set or clear a breakpoint at that line. Alternatively, you can click the Script Breakpoints Display button to
display the Script Breakpoints window and set or clear breakpoints in this window as described in “Script
Breakpoints window” on page 18.
Setting breakpoints in JavaScript code
Adding the debugger statement to a script sets an unconditional breakpoint. For example, the following code
causes the script to halt and display the JavaScript Debugger as soon as it enters the setupBox function.
function setupBox(box) {
// break unconditionally at the next line
debugger;

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box.width = 48;
box.height = 48;
box.url = "none";
}
To execute a breakpoint in runtime code, call the $.bp() method, as shown in the following example:
function setupBox(box) {
box.width = (box.width == undefined) ? $.bp() : 48;
box.height = (box.height == undefined) ? $.bp() : 48;
box.url = (box.url == undefined) ? $.bp() : "none";
}
This example breaks into the JavaScript Debugger if any of the width, height, or url attributes of the custom
element are undefined. Of course, you wouldn’t put bp method calls into production code—it’s more appro-
priate for shipping code to set default values for undefined properties, as the previous example does.
Script Breakpoints window
Display of the Script Breakpoints window is controlled by the Script Breakpoints button in the JavaScript
Debugger. This window displays all defined breakpoints. This window does not display temporary break-
points or breakpoints defined by the debugger statement in JavaScript code.
The Script Breakpoints window provides the following controls:
•The Line field contains the line number of the breakpoint.
•The Condition field may contain a JavaScript expression to evaluate when the breakpoint is reached. If the
expression evaluates to false, the breakpoint is not executed.
•Breakpoints set in this window persist across multiple executions of a script. When the application quits or
a script is reloaded, it removes all breakpoints.
To set a breakpoint in the Script Breakpoints window:
1Click New to create a new breakpoint, or click the breakpoint that you wish to edit.
2Enter a line number in the Line Number field, or change the existing line number.
3Optionally, enter a condition such as (i>5) in the Condition field. This can be any valid JavaScript
expression. If the result of evaluating the expression is true, the breakpoint activates.
The $ object
The $ object (Debugger Object) provides properties and methods you can use to debug your JavaScript code.
For example, you can call its methods to set or clear breakpoints programmatically, or to change the language
flavor of the script currently executing. It also provides properties that hold information about the version of
the host platform’s operating system.
Note: The $ object is not a standard JavaScript object.
Properties
Name Type Description
error Error Retrieve the last runtime error. Reading this property returns an Error
object containing information about the last runtime error.

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Debug output method
write (text, …);
writeln (text, …);
Write the given string to the Debug Output window. The writeln method appends a New Line character to its
arguments.
Parameters
Returns
None.
Clear breakpoint method
clearbp (scriptletName, line);
Clear a breakpoint. The breakpoint is defined by the name of the scriptlet or function and the line number. If
the scriptlet name is the empty string or is missing, the name of the currently executing scriptlet is used. If the
line number is zero or not supplied, the current line number is used. Thus, the call $.clearbp() without param-
eters clears a breakpoint at the current position.
The special string "NEXTCALL" as the scriptlet name causes the engine to clear a breakpoint at the next
function call.
Parameters
Returns
None.
Execute breakpoint method
bp([condition]);
Execute a breakpoint at the current position. Optionally, a condition may be supplied. The condition is a
JavaScript expression string that is evaluated before the breakpoint is executed. The breakpoint is executed
only if the expression returns true. If no condition is given, the use of the debugger statement is recommended
instead as it is a more widely supported JavaScript standard statement.
version String Returns the version number of the JavaScript engine as a three-part num-
ber like e.g."3.1.11". Read only.
os String Outputs the current operating system version. Read only.
text String All parameters are concatenated to a single string.
scriptletName String The name of the scriptlet where the breakpoint is to be cleared.
line Number The line number where the breakpoint is to be cleared.

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Parameters
Returns
None.
Garbage collection method
gc ()
Initiate a garbage collection. Garbage collection is the process by which the JavaScript interpreter cleans up
memory it is no longer using. This is done automatically. Occasionally when you’re debugging a script, it may
be useful to call this process.
Returns
None.
condition String An optional JavaScript expression string that is evaluated before the
breakpoint is executed.The expression needs to evaluate to the equivalent
of true in order to activate the breakpoint.