Adobe Illustrator Scripting

Expert guidance for automating Adobe Illustrator through ExtendScript (JavaScript/JSX). This skill covers the Illustrator scripting object model, all major API objects, code patterns, and best practices for writing production-quality .jsx scripts.

Bundled Assets

• references/object-model-quick-reference.md: Use this as a quick lookup for the Illustrator scripting object model, common document and page item types, and related DOM concepts while writing or debugging scripts.
• scripts/: Contains example Illustrator automation scripts you can use as starting points or implementation patterns for common tasks such as document manipulation, exports, batch processing, and DOM usage. Review and adapt these examples when you need working JSX patterns or want to compare behavior while debugging.

When to Use This Skill

• Writing new Illustrator automation scripts (.jsx or .js files)
• Debugging or fixing existing Illustrator ExtendScript code
• Manipulating documents, layers, page items, paths, text, or colors programmatically
• Batch-processing Illustrator files or generating artwork from data
• Exporting documents to various formats (PDF, SVG, PNG, EPS, etc.)
• Working with the Illustrator DOM (Application, Document, Layer, PathItem, TextFrame, etc.)
• Creating data-driven graphics using variables and datasets
• Automating print workflows with scripted print options

Prerequisites

• Adobe Illustrator CC or later installed
• Basic JavaScript knowledge (ExtendScript is ES3-based with Adobe extensions)
• Scripts are executed via File > Scripts > Other Scripts, the Scripts menu, or placed in the Startup Scripts folder
• The ExtendScript Toolkit (ESTK) or any text editor can be used to write .jsx files

Scripting Environment

Language and File Extensions

This skill focuses on ExtendScript/JavaScript as the cross-platform, most widely used option.

Executing Scripts

• Scripts menu: File > Scripts lists scripts from the application scripts folder
• Other Scripts: File > Scripts > Other Scripts to browse and run any .jsx file
• Startup Scripts: Place scripts in the Startup Scripts folder to run automatically on launch
• Target directive: Begin scripts with #target illustrator when running from ESTK or external tools
• #targetengine directive: Use #targetengine "session" to persist variables across script executions
• External invocation: Scripts are frequently launched from outside Illustrator — by shell scripts, task runners, CI jobs, ExtendScript Toolkit (ExtendScript Toolkit.exe -run script.jsx), or BridgeTalk messages from other Adobe apps. See External Invocation & Argument Passing.

Naming Conventions (JavaScript)

• Objects and properties use camelCase: activeDocument, pathItems, textFrames
• The app global references the Application object
• Collection indices are zero-based: documents[0] is the frontmost document
• Use typename property to identify object types at runtime

Object Model Overview

The Illustrator DOM follows a strict containment hierarchy:

Application (app)
├── activeDocument / documents[]
│   ├── layers[]
│   │   ├── pageItems[] (all artwork)
│   │   ├── pathItems[]
│   │   ├── compoundPathItems[]
│   │   ├── textFrames[]
│   │   ├── placedItems[]
│   │   ├── rasterItems[]
│   │   ├── meshItems[]
│   │   ├── pluginItems[]
│   │   ├── graphItems[]
│   │   ├── symbolItems[]
│   │   ├── nonNativeItems[]
│   │   ├── legacyTextItems[]
│   │   └── groupItems[]
│   ├── artboards[]
│   ├── views[]
│   ├── selection (array of selected items)
│   ├── swatches[], spots[], gradients[], patterns[]
│   ├── graphicStyles[], brushes[], symbols[]
│   ├── textFonts[] (via app.textFonts)
│   ├── stories[], characterStyles[], paragraphStyles[]
│   ├── variables[], datasets[]
│   └── inkList[], printOptions
├── preferences
├── printerList[]
└── textFonts[]

Top-Level Objects

• Application (app): The root object. Provides access to documents, preferences, fonts, and printers. Key properties: activeDocument, documents, textFonts, printerList, userInteractionLevel, version.
• Document: Represents an open .ai file. Key properties: layers, pageItems, selection, activeLayer, width, height, rulerOrigin, documentColorSpace. Key methods: saveAs(), exportFile(), close(), print().
• Layer: A drawing layer. Key properties: pageItems, pathItems, textFrames, visible, locked, opacity, name, zOrderPosition, color.

Measurement Units and Coordinates

Units

All scripting API values use points (72 points = 1 inch). Convert other units:

Kerning, tracking, and aki properties use em units (thousandths of an em, proportional to font size).

Coordinate System

• For scripted documents, the origin (0,0) is at the bottom-left of the artboard
• X increases left to right; Y increases bottom to top
• The position property of a page item is the top-left corner of its bounding box as [x, y]
• Maximum page item width/height: 16348 points

Art Item Bounds

Every page item has three bounding rectangles:

• geometricBounds: Excludes stroke width [left, top, right, bottom]
• visibleBounds: Includes stroke width
• controlBounds: Includes control/direction points

Working with Documents

Creating and Opening

// Create a new document
var doc = app.documents.add();

// Create with a preset
var preset = new DocumentPreset();
preset.width = 612;  // 8.5 inches
preset.height = 792; // 11 inches
preset.colorMode = DocumentColorSpace.CMYK;
var doc = app.documents.addDocument("Print", preset);

// Open an existing file
var fileRef = new File("/path/to/file.ai");
var doc = app.open(fileRef);

Saving and Exporting

// Save as Illustrator format
var saveOpts = new IllustratorSaveOptions();
saveOpts.compatibility = Compatibility.ILLUSTRATOR17; // CC
doc.saveAs(new File("/path/to/output.ai"), saveOpts);

// Export as PDF
var pdfOpts = new PDFSaveOptions();
pdfOpts.compatibility = PDFCompatibility.ACROBAT7;
pdfOpts.preserveEditability = false;
doc.saveAs(new File("/path/to/output.pdf"), pdfOpts);

// Export as PNG
var pngOpts = new ExportOptionsPNG24();
pngOpts.horizontalScale = 300;
pngOpts.verticalScale = 300;
pngOpts.transparency = true;
doc.exportFile(new File("/path/to/output.png"), ExportType.PNG24, pngOpts);

// Export as SVG
var svgOpts = new ExportOptionsSVG();
svgOpts.fontType = SVGFontType.OUTLINEFONT;
doc.exportFile(new File("/path/to/output.svg"), ExportType.SVG, svgOpts);

Working with Paths and Shapes

Built-in Shape Methods

The pathItems collection provides convenience methods for common shapes:

var doc = app.activeDocument;
var layer = doc.activeLayer;

// Rectangle: rectangle(top, left, width, height)
var rect = layer.pathItems.rectangle(500, 100, 200, 150);

// Rounded rectangle: roundedRectangle(top, left, width, height, hRadius, vRadius)
var rrect = layer.pathItems.roundedRectangle(500, 100, 200, 150, 20, 20);

// Ellipse: ellipse(top, left, width, height)
var oval = layer.pathItems.ellipse(400, 200, 100, 100);

// Polygon: polygon(centerX, centerY, radius, sides)
var hex = layer.pathItems.polygon(300, 300, 50, 6);

// Star: star(centerX, centerY, radius, innerRadius, points)
var star = layer.pathItems.star(300, 300, 50, 25, 5);

Freeform Paths Using Coordinate Arrays

var doc = app.activeDocument;
var path = doc.pathItems.add();
path.setEntirePath([[100, 100], [200, 200], [300, 100]]);
path.closed = false;
path.stroked = true;
path.strokeWidth = 2;

Freeform Paths Using PathPoint Objects

var doc = app.activeDocument;
var path = doc.pathItems.add();

var point1 = path.pathPoints.add();
point1.anchor = [100, 100];
point1.leftDirection = [100, 100];
point1.rightDirection = [150, 150];
point1.pointType = PointType.SMOOTH;

var point2 = path.pathPoints.add();
point2.anchor = [300, 100];
point2.leftDirection = [250, 150];
point2.rightDirection = [300, 100];
point2.pointType = PointType.SMOOTH;

path.closed = false;

Path Properties

var item = doc.pathItems[0];
item.filled = true;
item.stroked = true;
item.strokeWidth = 1.5;
item.strokeCap = StrokeCap.ROUNDENDCAP;
item.strokeJoin = StrokeJoin.ROUNDENDJOIN;
item.opacity = 80;
item.closed = true;

Working with Colors

Color Objects

// RGB Color (values 0-255)
var red = new RGBColor();
red.red = 255;
red.green = 0;
red.blue = 0;

// CMYK Color (values 0-100)
var cyan = new CMYKColor();
cyan.cyan = 100;
cyan.magenta = 0;
cyan.yellow = 0;
cyan.black = 0;

// Grayscale (0-100, 0 = black)
var gray = new GrayColor();
gray.gray = 50;

// Lab Color
var lab = new LabColor();
lab.l = 50;
lab.a = 20;
lab.b = -30;

// No color (transparent)
var none = new NoColor();

Applying Colors

var item = doc.pathItems[0];
item.fillColor = red;
item.strokeColor = cyan;

// Gradient fill
var gradient = doc.gradients.add();
gradient.type = GradientType.LINEAR;
gradient.gradientStops[0].color = red;
gradient.gradientStops[1].color = cyan;

var gradColor = new GradientColor();
gradColor.gradient = gradient;
item.fillColor = gradColor;

Spot Colors and Swatches

// Create a spot color
var spot = doc.spots.add();
spot.name = "My Spot Color";
spot.color = red; // Base color definition

var spotColor = new SpotColor();
spotColor.spot = spot;
spotColor.tint = 100;

item.fillColor = spotColor;

// Access a swatch by name
var swatch = doc.swatches.getByName("PANTONE 185 C");
item.fillColor = swatch.color;

Working with Text

Text Frame Types

var doc = app.activeDocument;

// Point text
var pointText = doc.textFrames.add();
pointText.contents = "Hello World!";
pointText.position = [100, 500];

// Area text (text inside a path)
var rectPath = doc.pathItems.rectangle(500, 100, 200, 100);
var areaText = doc.textFrames.areaText(rectPath);
areaText.contents = "Text inside a rectangle shape.";

// Path text (text along a path)
var curvePath = doc.pathItems.add();
curvePath.setEntirePath([[50, 300], [150, 400], [250, 300]]);
var pathText = doc.textFrames.pathText(curvePath);
pathText.contents = "Text on a path";

Character and Paragraph Formatting

var tf = doc.textFrames[0];
var textRange = tf.textRange;

// Character attributes
var charAttr = textRange.characterAttributes;
charAttr.size = 24;           // Font size in points
charAttr.textFont = app.textFonts.getByName("ArialMT");
charAttr.fillColor = red;
charAttr.tracking = 50;       // Em units
charAttr.horizontalScale = 100;
charAttr.verticalScale = 100;
charAttr.baselineShift = 0;

// Paragraph attributes
var paraAttr = textRange.paragraphAttributes;
paraAttr.justification = Justification.CENTER;
paraAttr.firstLineIndent = 0;
paraAttr.leftIndent = 0;
paraAttr.spaceBefore = 0;
paraAttr.spaceAfter = 0;

Accessing Text Content

var tf = doc.textFrames[0];

// Access sub-ranges
var firstChar = tf.characters[0];
var firstWord = tf.words[0];
var firstPara = tf.paragraphs[0];
var firstLine = tf.lines[0];

// Modify specific ranges
tf.words[0].characterAttributes.size = 36;
tf.paragraphs[0].paragraphAttributes.justification = Justification.LEFT;

Threading Text Frames

var frame1 = doc.textFrames.areaText(path1);
var frame2 = doc.textFrames.areaText(path2);

// Link frames so text flows from frame1 to frame2
frame1.nextFrame = frame2;

// Stories represent the full text across threaded frames
var storyCount = doc.stories.length;
var fullText = doc.stories[0].textRange.contents;

Working with Layers

var doc = app.activeDocument;

// Create a layer
var newLayer = doc.layers.add();
newLayer.name = "Background";
newLayer.visible = true;
newLayer.locked = false;
newLayer.opacity = 100;

// Access existing layers
var topLayer = doc.layers[0];
var layerByName = doc.layers.getByName("Background");

// Move items between layers
var item = doc.pathItems[0];
item.move(newLayer, ElementPlacement.PLACEATBEGINNING);

// Reorder layers
newLayer.zOrder(ZOrderMethod.SENDTOBACK);

Working with Selections

// Get current selection
var sel = app.activeDocument.selection;

// Iterate selected items
for (var i = 0; i < sel.length; i++) {
    var item = sel[i];
    // Check type using typename
    if (item.typename === "PathItem") {
        item.fillColor = red;
    } else if (item.typename === "TextFrame") {
        item.contents = "Modified";
    }
}

// Select an item programmatically
doc.pathItems[0].selected = true;

// Deselect all
doc.selection = null;

Working with Symbols

// Place a symbol instance
var sym = doc.symbols.getByName("MySymbol");
var instance = doc.symbolItems.add(sym);
instance.position = [200, 400];

// Access symbol definition
var symDef = instance.symbol;

// Break link to symbol (expand to regular art)
instance.breakLink();

Transformations

var item = doc.pathItems[0];

// Rotate 45 degrees around center
item.rotate(45);

// Scale to 50% width, 75% height
item.resize(50, 75);

// Translate (move) by 100 points right and 50 points up
item.translate(100, 50);

// Using a transformation matrix
var matrix = app.getIdentityMatrix();
matrix = app.concatenateRotationMatrix(matrix, 30);
matrix = app.concatenateScaleMatrix(matrix, 150, 150);
item.transform(matrix);

Working with Artboards

var doc = app.activeDocument;

// Access artboards
var ab = doc.artboards[0];
var rect = ab.artboardRect; // [left, top, right, bottom]

// Create a new artboard
var newAB = doc.artboards.add([0, 0, 612, 792]); // Letter size
newAB.name = "Page 2";

// Set active artboard
doc.artboards.setActiveArtboardIndex(1);

Data-Driven Graphics (Variables and Datasets)

// Variables link document items to data fields
var v = doc.variables.add();
v.kind = VariableKind.TEXTUAL;
v.name = "headline";

// Link a text frame to the variable
var tf = doc.textFrames[0];
tf.contentVariable = v;

// Create datasets for batch content
var ds = doc.dataSets.add();
ds.name = "Version 1";
// Dataset captures current variable bindings

// Switch datasets to swap content
doc.dataSets[0].display();

Printing

var doc = app.activeDocument;
var opts = new PrintOptions();

opts.printPreset = "Default";

// Paper options
var paperOpts = new PrintPaperOptions();
paperOpts.name = "Letter";
opts.paperOptions = paperOpts;

// Job options
var jobOpts = new PrintJobOptions();
jobOpts.copies = 1;
jobOpts.designation = PrintArtworkDesignation.VISIBLELAYERS;
opts.jobOptions = jobOpts;

doc.print(opts);

User Interaction Levels

Control whether Illustrator shows dialogs during script execution:

// Suppress all dialogs
app.userInteractionLevel = UserInteractionLevel.DONTDISPLAYALERTS;

// Perform operations that might prompt dialogs...
doc.close(SaveOptions.DONOTSAVECHANGES);

// Restore dialog display
app.userInteractionLevel = UserInteractionLevel.DISPLAYALERTS;

Working with Methods (JavaScript-Specific)

When calling methods with multiple optional parameters, use undefined to skip middle parameters:

// rotate(angle, [changePositions], [changeFillPatterns], [changeFillGradients], ...)
item.rotate(30, undefined, undefined, true);

External Invocation & Argument Passing

Illustrator scripts are routinely launched from outside the application — shell scripts, schedulers, build pipelines, ExtendScript Toolkit, or BridgeTalk messages from other Creative Cloud apps. The execution environment under those launchers differs from the in-application File > Scripts path in several ways that frequently break otherwise-correct code.

arguments[] Is Unreliable Under External Launchers

ExtendScript Toolkit's -run invocation and BridgeTalk.send() do not forward arbitrary launcher arguments into the script's top-level arguments[] array. In many configurations the array contains a single [object BridgeTalk] element instead of the values the caller passed, as demonstrated below:

// At top of script
var passed = (typeof arguments !== "undefined") ? arguments : [];
for (var i = 0; i < passed.length; i++) {
    $.writeln("arg[" + i + "] = " + passed[i]);
    // Often prints: arg[0] = [object BridgeTalk]
}

Do not rely on arguments[] for required inputs when the script is launched externally. Use one of the following more reliable channels.

Sidecar File for Parameters

When a script fails under an external launcher and the source of the error is not obvious, fall back to a sidecar file: have the caller write a small text file at a known absolute path, and read it on startup. This works regardless of launcher quirks and is easy to inspect after a failed run.

var SIDECAR_PATH = "C:/Users/userName/job.args.txt";

function readSidecar(path) {
    var f = new File(path);
    if (!f.exists || !f.open("r")) return null;
    var lines = [];
    while (!f.eof) {
        var ln = f.readln();
        if (ln && !/^\s*$/.test(ln)) lines.push(ln);
    }
    f.close();
    return {
        input:  lines[0],
        output: lines[1],
        mode:   lines[2]
    };
}

A key=value format is equally workable and avoids positional fragility:

input=C:/path/to/input.ai
output=C:/path/to/output.pdf
mode=preview

Environment Variables

$.getenv("NAME") returns environment variables visible to Illustrator's process, not the launcher's. If the launcher needs Illustrator to see a value, it must set the variable system-wide or in Illustrator's parent environment before launching. For per-invocation values, prefer a sidecar file.

$.fileName and File($.fileName).parent

Under in-application execution, $.fileName is the absolute path of the running script and File($.fileName).parent yields the script's folder. Under some external launchers (notably ESTK -run) $.fileName can be empty, causing relative path resolution to silently fail.

// Fragile: returns null under some launchers
var here = $.fileName ? File($.fileName).parent : null;
var sidecar = here ? new File(here.fsName + "/job.args.txt") : null;

// Robust: hardcode a known absolute path or fall back to a stable location
var sidecar = new File("C:/Users/userName/job.args.txt");
if (!sidecar.exists) sidecar = new File(Folder.temp.fsName + "/job.args.txt");

Diagnostic Logging to an Absolute Path

Silent failures are common because dialogs are suppressed and the launcher may not surface $.writeln output. Write a plain-text log to a known absolute path so a run can be inspected after the fact. Create the parent folder on demand so the first call cannot fail for a missing directory.

var LOG_PATH = "C:/Users/userName/logs/job.log";

function log(msg) {
    try {
        var f = new File(LOG_PATH);
        try { if (!f.parent.exists) f.parent.create(); } catch (eDir) {}
        if (f.open("a")) {
            f.writeln("[" + new Date() + "] " + msg);
            f.close();
        }
    } catch (e) {}
}

Wrap the Entry Point in try { ... } catch

Externally launched scripts often fail without any visible indication. A top-level try/catch that writes the error to the log file converts silent failures into a single inspectable line.

try {
    main();
} catch (err) {
    log("FATAL: " + err + (err && err.line ? " line=" + err.line : ""));
}

Suppress User Interaction

External callers cannot answer dialogs. Disable them before any DOM work and avoid alert() / confirm() / prompt() entirely in scripts that may be launched headlessly.

app.userInteractionLevel = UserInteractionLevel.DONTDISPLAYALERTS;

Save Explicitly

Closing or letting Illustrator return to its idle state does not save the working file. After all DOM edits, call doc.saveAs(...) (or doc.save()) explicitly and log whether it succeeded.

var opts = new IllustratorSaveOptions();
opts.compatibility = Compatibility.ILLUSTRATOR17;
doc.saveAs(new File(doc.fullName.fsName), opts);

Common Patterns

Iterate All Page Items in a Document

function processAllItems(doc) {
    for (var i = 0; i < doc.pageItems.length; i++) {
        var item = doc.pageItems[i];
        // Process based on type
        switch (item.typename) {
            case "PathItem":
                // handle path
                break;
            case "TextFrame":
                // handle text
                break;
            case "GroupItem":
                // handle group (may contain nested items)
                break;
        }
    }
}

Recursively Unlock Layers and Groups Before Editing

A locked layer or any locked ancestor (parent group, clip group, sublayer) will cause edits to throw Error: Target layer cannot be modified. Walk the full hierarchy and clear locked / hidden flags before performing DOM modifications.

function unlockAll(doc) {
    function visitLayers(layers) {
        for (var i = 0; i < layers.length; i++) {
            var lyr = layers[i];
            try { lyr.locked = false; lyr.visible = true; } catch (e) {}
            visitItems(lyr);
            if (lyr.layers && lyr.layers.length) visitLayers(lyr.layers);
        }
    }
    function visitItems(container) {
        var items = container.pageItems;
        for (var j = 0; j < items.length; j++) {
            var it = items[j];
            try { it.locked = false; it.hidden = false; } catch (e) {}
            if (it.typename === "GroupItem") visitItems(it);
        }
    }
    visitLayers(doc.layers);
}

Replacing the File Behind a Linked Image (Relink)

PlacedItem.file = newFile replaces a linked image while preserving the parent, stacking order, and (after re-applying) the bounds. RasterItem does not expose a writable file property, so when a placeholder is a raster you must add a fresh PlacedItem in the same parent, copy the bounds, then remove the original.

function relinkOrRebuild(item, newFile) {
    var bounds = item.geometricBounds.slice();
    var parent = item.parent;
    var name   = item.name;

    if (item.typename === "PlacedItem") {
        item.file = newFile;
        item.geometricBounds = bounds;
        return item;
    }

    // RasterItem path: rebuild as a linked PlacedItem in the same parent.
    var fresh = parent.placedItems.add();
    fresh.file = newFile;
    fresh.geometricBounds = bounds;
    if (name) try { fresh.name = name; } catch (e) {}
    fresh.move(item, ElementPlacement.PLACEBEFORE);
    item.remove();
    return fresh;
}

Placing SVG Content (Copy/Paste Pattern)

PlacedItem.file accepts raster formats and AI/PDF, but not SVG. Setting it to an .svg File throws Unable to set placed item's file, is the file path provided valid?. The reliable way to bring SVG artwork into a document is to open the SVG as a separate document, select all, copy, close, and paste into the working document.

function placeSVG(targetDoc, svgFile, targetLayer) {
    var donor = app.open(svgFile);
    app.executeMenuCommand("selectall");
    app.executeMenuCommand("copy");
    donor.close(SaveOptions.DONOTSAVECHANGES);

    app.activeDocument = targetDoc;
    targetDoc.activeLayer = targetLayer;
    app.executeMenuCommand("pasteFront");

    var sel = targetDoc.selection;
    if (!sel || sel.length === 0) return null;
    if (sel.length === 1) return sel[0];

    // Multiple pasted items: group them so callers get a single handle.
    var group = targetLayer.groupItems.add();
    for (var i = sel.length - 1; i >= 0; i--) {
        sel[i].move(group, ElementPlacement.PLACEATBEGINNING);
    }
    return group;
}

Finding a Clipping Path Inside a Mask Group

Clip groups expose their clipping shape as a child PathItem (or, less commonly, a child of a CompoundPathItem) with clipping === true. The clip's geometricBounds give the visible frame to size or center content against.

function findClipPath(group) {
    var items = group.pageItems;
    for (var i = 0; i < items.length; i++) {
        var it = items[i];
        try {
            if (it.typename === "PathItem" && it.clipping) return it;
            if (it.typename === "CompoundPathItem") {
                for (var j = 0; j < it.pathItems.length; j++) {
                    if (it.pathItems[j].clipping) return it;
                }
            }
        } catch (e) {}
    }
    return null;
}

Cover-Fit and Contain-Fit Sizing

To make an image fully cover a rectangle (any overflow hidden by a mask), use the larger of the width/height ratios. To make it fit entirely inside, use the smaller. A bleed factor (e.g. 1.10) lets a cover image extend slightly past the clip edge.

function fitItemToRect(item, rect, mode, bleed) {
    // rect = [L, T, R, B] (Illustrator: T > B)
    var rw = rect[2] - rect[0];
    var rh = rect[1] - rect[3];
    var ib = item.geometricBounds;
    var iw = ib[2] - ib[0];
    var ih = ib[1] - ib[3];
    if (iw <= 0 || ih <= 0) return;

    var sx = rw / iw;
    var sy = rh / ih;
    var s  = (mode === "cover" ? Math.max(sx, sy) : Math.min(sx, sy))
           * (bleed || 1);
    item.resize(s * 100, s * 100);

    var cx = (rect[0] + rect[2]) / 2;
    var cy = (rect[1] + rect[3]) / 2;
    var b  = item.geometricBounds;
    var w  = b[2] - b[0];
    var h  = b[1] - b[3];
    item.position = [cx - w / 2, cy + h / 2];
}

Batch Process Files in a Folder

var folder = Folder.selectDialog("Select folder of .ai files");
if (folder) {
    var files = folder.getFiles("*.ai");
    for (var i = 0; i < files.length; i++) {
        var doc = app.open(files[i]);
        // Process each document...
        doc.close(SaveOptions.DONOTSAVECHANGES);
    }
}

Error Handling

try {
    var doc = app.activeDocument;
    var layer = doc.layers.getByName("NonExistentLayer");
} catch (e) {
    alert("Error: " + e.message);
    // e.message, e.line, e.fileName available
}

Troubleshooting

• "undefined is not an object": Usually means the collection is empty or the index is out of bounds. Check .length before accessing items.
• Script runs but nothing changes visually: Call app.redraw() to force a screen refresh after modifications.
• Color mode mismatch: Document color space (RGB vs CMYK) must match color objects. Use doc.documentColorSpace to check.
• Position seems wrong: Remember scripted documents use bottom-left origin with Y increasing upward. The position property is the top-left of the bounding box.
• Text not appearing: Ensure the text frame has a non-zero size. For point text, set position; for area text, provide a valid path to areaText().
• File paths on Windows: Use forward slashes (/) or double backslashes (\\) in path strings, or use the File object constructor.
• Dialog boxes interrupting batch scripts: Set app.userInteractionLevel = UserInteractionLevel.DONTDISPLAYALERTS before batch operations.
• Collections use getByName(): Many collection objects support getByName("name") which throws an error if not found; wrap in try/catch.
• "Target layer cannot be modified": A locked layer, sublayer, or parent group (often a clip group like Cover_Mask) is blocking the edit. Recursively clear locked and hidden across the document before modifying. See Recursively Unlock Layers and Groups.
• "Unable to set placed item's file, is the file path provided valid?": The file exists and the path is correct, but PlacedItem.file does not accept the format. SVG is the most common cause — use the open / copy / paste pattern instead.
• RasterItem.file = newFile does nothing or throws: RasterItem does not expose a writable file property. Add a new PlacedItem to the same parent, restore the bounds and name, then .remove() the raster.
• arguments[0] is [object BridgeTalk] (or empty): The script was launched through ESTK -run or a BridgeTalk message; positional arguments are not forwarded. Use a sidecar file at a known absolute path. See External Invocation & Argument Passing.
• $.fileName is empty: Same external-launcher cause. Do not derive resource paths from $.fileName in scripts that may be invoked headlessly — use absolute paths or Folder.temp.
• Script appears to do nothing: Almost always either a locked ancestor, suppressed dialogs swallowing the error, or a missing explicit saveAs after edits. Add a top-level try/catch that logs to an absolute path to confirm execution and capture the error.
• item.resize(sx, sy) recentered the artwork unexpectedly: resize defaults to scaling around the item's center (Transformation.CENTER). Pass an explicit scaleAbout argument or follow with translate(dx, dy) to reposition.

Scripting Constants Reference

Common enumeration constants used across the API:

JavaScript Object Reference (Complete API Object List)

The Illustrator JavaScript API contains the following objects, grouped by category:

Core Objects

Application, Document, Documents, DocumentPreset, Layer, Layers, PageItem, PageItems, View, Views, Preferences

Path and Shape Objects

PathItem, PathItems, PathPoint, PathPoints, CompoundPathItem, CompoundPathItems, GroupItem, GroupItems

Text Objects

TextFrame, TextRange, TextRanges, TextPath, Characters, Words, Paragraphs, Lines, InsertionPoint, InsertionPoints, Story, Stories, CharacterAttributes, ParagraphAttributes, CharacterStyle, CharacterStyles, ParagraphStyle, ParagraphStyles, TextFont, TextFonts, TabStopInfo

Color Objects

RGBColor, CMYKColor, GrayColor, LabColor, NoColor, SpotColor, Spot, Spots, PatternColor, GradientColor, Color, Gradient, Gradients, GradientStop, GradientStops

Swatch and Style Objects

Swatch, Swatches, SwatchGroup, SwatchGroups, GraphicStyle, GraphicStyles, Pattern, Patterns, Brush, Brushes

Symbol Objects

Symbol, Symbols, SymbolItem, SymbolItems

Artboard Objects

Artboard, Artboards

Placed and Raster Objects

PlacedItem, PlacedItems, RasterItem, RasterItems, MeshItem, MeshItems, GraphItem, GraphItems, PluginItem, PluginItems, NonNativeItem, NonNativeItems, LegacyTextItem, LegacyTextItems

Data-Driven Objects

Variable, Variables, Dataset, Datasets

Matrix and Transform Objects

Matrix

Tag Objects

Tag, Tags

Tracing Objects

TracingObject, TracingOptions

Save and Export Options

IllustratorSaveOptions, EPSSaveOptions, PDFSaveOptions, FXGSaveOptions, ExportOptionsAutoCAD, ExportOptionsFlash, ExportOptionsGIF, ExportOptionsJPEG, ExportOptionsPhotoshop, ExportOptionsPNG8, ExportOptionsPNG24, ExportOptionsSVG, ExportOptionsTIFF

Open Options

OpenOptions, OpenOptionsAutoCAD, OpenOptionsFreeHand, OpenOptionsPhotoshop, PDFFileOptions, PhotoshopFileOptions

Print Objects

PrintOptions, PrintJobOptions, PrintPaperOptions, PrintColorManagementOptions, PrintColorSeparationOptions, PrintCoordinateOptions, PrintFlattenerOptions, PrintFontOptions, PrintPageMarksOptions, PrintPostScriptOptions, Printer, PrinterInfo, Paper, PaperInfo, PPDFile, PPDFileInfo, Ink, InkInfo, Screen, ScreenInfo, ScreenSpotFunction

Image and Rasterize Options

ImageCaptureOptions, RasterEffectOptions, RasterizeOptions

References

• Changelog - Recent scripting API changes (CC 2020 added Document.getPageItemFromUuid and PageItem.uuid; CC 2017 added Application.getIsFileOpen)
• Illustrator Scripting Guide - Full community-maintained documentation