Prefer instanceof Dict rather than calling isDict() with one argument

Unless you actually need to check that something is both a `Dict` and also of the *correct* type, using `instanceof Dict` directly should be a tiny bit more efficient since it avoids one function call and an unnecessary `undefined` check.

This patch uses ESLint to enforce this, since we obviously still want to keep the `isDict` helper function for where it makes sense.

.eslintrc

@@ -183,6 +183,10 @@
         "selector": "CallExpression[callee.name='isCmd'][arguments.length<2]",
         "message": "Use `instanceof Cmd` rather than `isCmd()` with one argument.",
       },
+      {
+        "selector": "CallExpression[callee.name='isDict'][arguments.length<2]",
+        "message": "Use `instanceof Dict` rather than `isDict()` with one argument.",
+      },
       {
         "selector": "NewExpression[callee.name='Cmd']",
         "message": "Use `Cmd.get()` rather than `new Cmd()`.",

src/core/annotation.js

@@ -39,7 +39,7 @@ import {
   createDefaultAppearance,
   parseDefaultAppearance,
 } from "./default_appearance.js";
-import { Dict, isDict, isName, Name, Ref, RefSet } from "./primitives.js";
+import { Dict, isName, Name, Ref, RefSet } from "./primitives.js";
 import { BaseStream } from "./base_stream.js";
 import { bidi } from "./bidi.js";
 import { Catalog } from "./catalog.js";
@@ -95,7 +95,7 @@ class AnnotationFactory {
     pageIndex = -1
   ) {
     const dict = xref.fetchIfRef(ref);
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       return undefined;
     }
 
@@ -209,7 +209,7 @@ class AnnotationFactory {
   static async _getPageIndex(xref, ref, pdfManager) {
     try {
       const annotDict = await xref.fetchIfRefAsync(ref);
-      if (!isDict(annotDict)) {
+      if (!(annotDict instanceof Dict)) {
         return -1;
       }
       const pageRef = annotDict.getRaw("P");
@@ -636,7 +636,7 @@ class Annotation {
     }
 
     this.borderStyle = new AnnotationBorderStyle();
-    if (!isDict(borderStyle)) {
+    if (!(borderStyle instanceof Dict)) {
       return;
     }
     if (borderStyle.has("BS")) {
@@ -681,7 +681,7 @@ class Annotation {
     this.appearance = null;
 
     const appearanceStates = dict.get("AP");
-    if (!isDict(appearanceStates)) {
+    if (!(appearanceStates instanceof Dict)) {
       return;
     }
 
@@ -691,7 +691,7 @@ class Annotation {
       this.appearance = normalAppearanceState;
       return;
     }
-    if (!isDict(normalAppearanceState)) {
+    if (!(normalAppearanceState instanceof Dict)) {
       return;
     }
 
@@ -1418,7 +1418,7 @@ class WidgetAnnotation extends Annotation {
     const { xref } = evaluator;
 
     const dict = xref.fetchIfRef(this.ref);
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       return null;
     }
 
@@ -2085,7 +2085,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     }
 
     const dict = evaluator.xref.fetchIfRef(this.ref);
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       return null;
     }
 
@@ -2131,7 +2131,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     }
 
     const dict = evaluator.xref.fetchIfRef(this.ref);
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       return null;
     }
 
@@ -2158,7 +2158,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
         parentBuffer = [`${this.parent.num} ${this.parent.gen} obj\n`];
         writeDict(parent, parentBuffer, parentTransform);
         parentBuffer.push("\nendobj\n");
-      } else if (isDict(this.parent)) {
+      } else if (this.parent instanceof Dict) {
         this.parent.set("V", name);
       }
     }
@@ -2250,12 +2250,12 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
 
   _processCheckBox(params) {
     const customAppearance = params.dict.get("AP");
-    if (!isDict(customAppearance)) {
+    if (!(customAppearance instanceof Dict)) {
       return;
     }
 
     const normalAppearance = customAppearance.get("N");
-    if (!isDict(normalAppearance)) {
+    if (!(normalAppearance instanceof Dict)) {
       return;
     }
 
@@ -2318,7 +2318,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     // The parent field's `V` entry holds a `Name` object with the appearance
     // state of whichever child field is currently in the "on" state.
     const fieldParent = params.dict.get("Parent");
-    if (isDict(fieldParent)) {
+    if (fieldParent instanceof Dict) {
       this.parent = params.dict.getRaw("Parent");
       const fieldParentValue = fieldParent.get("V");
       if (isName(fieldParentValue)) {
@@ -2328,11 +2328,11 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
 
     // The button's value corresponds to its appearance state.
     const appearanceStates = params.dict.get("AP");
-    if (!isDict(appearanceStates)) {
+    if (!(appearanceStates instanceof Dict)) {
       return;
     }
     const normalAppearance = appearanceStates.get("N");
-    if (!isDict(normalAppearance)) {
+    if (!(normalAppearance instanceof Dict)) {
       return;
     }
     for (const key of normalAppearance.getKeys()) {

src/core/catalog.js

@@ -120,7 +120,7 @@ class Catalog {
     let collection = null;
     try {
       const obj = this._catDict.get("Collection");
-      if (isDict(obj) && obj.size > 0) {
+      if (obj instanceof Dict && obj.size > 0) {
         collection = obj;
       }
     } catch (ex) {
@@ -136,7 +136,7 @@ class Catalog {
     let acroForm = null;
     try {
       const obj = this._catDict.get("AcroForm");
-      if (isDict(obj) && obj.size > 0) {
+      if (obj instanceof Dict && obj.size > 0) {
         acroForm = obj;
       }
     } catch (ex) {
@@ -208,7 +208,7 @@ class Catalog {
    */
   _readMarkInfo() {
     const obj = this._catDict.get("MarkInfo");
-    if (!isDict(obj)) {
+    if (!(obj instanceof Dict)) {
       return null;
     }
 
@@ -249,7 +249,7 @@ class Catalog {
    */
   _readStructTreeRoot() {
     const obj = this._catDict.get("StructTreeRoot");
-    if (!isDict(obj)) {
+    if (!(obj instanceof Dict)) {
       return null;
     }
     const root = new StructTreeRoot(obj);
@@ -259,7 +259,7 @@ class Catalog {
 
   get toplevelPagesDict() {
     const pagesObj = this._catDict.get("Pages");
-    if (!isDict(pagesObj)) {
+    if (!(pagesObj instanceof Dict)) {
       throw new FormatError("Invalid top-level pages dictionary.");
     }
     return shadow(this, "toplevelPagesDict", pagesObj);
@@ -283,7 +283,7 @@ class Catalog {
    */
   _readDocumentOutline() {
     let obj = this._catDict.get("Outlines");
-    if (!isDict(obj)) {
+    if (!(obj instanceof Dict)) {
       return null;
     }
     obj = obj.getRaw("First");
@@ -376,7 +376,7 @@ class Catalog {
    */
   _readPermissions() {
     const encrypt = this.xref.trailer.get("Encrypt");
-    if (!isDict(encrypt)) {
+    if (!(encrypt instanceof Dict)) {
       return null;
     }
 
@@ -654,7 +654,7 @@ class Catalog {
       const labelDict = nums.get(i);
 
       if (labelDict !== undefined) {
-        if (!isDict(labelDict)) {
+        if (!(labelDict instanceof Dict)) {
           throw new FormatError("PageLabel is not a dictionary.");
         }
 
@@ -799,7 +799,7 @@ class Catalog {
     const obj = this._catDict.get("ViewerPreferences");
     let prefs = null;
 
-    if (isDict(obj)) {
+    if (obj instanceof Dict) {
       for (const key in ViewerPreferencesValidators) {
         if (!obj.has(key)) {
           continue;
@@ -921,7 +921,7 @@ class Catalog {
     const obj = this._catDict.get("OpenAction");
     const openAction = Object.create(null);
 
-    if (isDict(obj)) {
+    if (obj instanceof Dict) {
       // Convert the OpenAction dictionary into a format that works with
       // `parseDestDictionary`, to avoid having to re-implement those checks.
       const destDict = new Dict(this.xref);
@@ -1337,7 +1337,7 @@ class Catalog {
           if (
             isRefsEqual(kidRef, pageRef) &&
             !isDict(node, "Page") &&
-            !(isDict(node) && !node.has("Type") && node.has("Contents"))
+            !(node instanceof Dict && !node.has("Type") && node.has("Contents"))
           ) {
             throw new FormatError(
               "The reference does not point to a /Page dictionary."
@@ -1346,7 +1346,7 @@ class Catalog {
           if (!node) {
             return null;
           }
-          if (!isDict(node)) {
+          if (!(node instanceof Dict)) {
             throw new FormatError("Node must be a dictionary.");
           }
           parentRef = node.getRaw("Parent");
@@ -1356,7 +1356,7 @@ class Catalog {
           if (!parent) {
             return null;
           }
-          if (!isDict(parent)) {
+          if (!(parent instanceof Dict)) {
             throw new FormatError("Parent must be a dictionary.");
           }
           return parent.getAsync("Kids");
@@ -1379,7 +1379,7 @@ class Catalog {
             }
             kidPromises.push(
               xref.fetchAsync(kid).then(function (obj) {
-                if (!isDict(obj)) {
+                if (!(obj instanceof Dict)) {
                   throw new FormatError("Kid node must be a dictionary.");
                 }
                 if (obj.has("Count")) {
@@ -1430,7 +1430,7 @@ class Catalog {
    */
   static parseDestDictionary(params) {
     const destDict = params.destDict;
-    if (!isDict(destDict)) {
+    if (!(destDict instanceof Dict)) {
       warn("parseDestDictionary: `destDict` must be a dictionary.");
       return;
     }
@@ -1444,14 +1444,14 @@ class Catalog {
     let action = destDict.get("A"),
       url,
       dest;
-    if (!isDict(action)) {
+    if (!(action instanceof Dict)) {
       if (destDict.has("Dest")) {
         // A /Dest entry should *only* contain a Name or an Array, but some bad
         // PDF generators ignore that and treat it as an /A entry.
         action = destDict.get("Dest");
       } else {
         action = destDict.get("AA");
-        if (isDict(action)) {
+        if (action instanceof Dict) {
           if (action.has("D")) {
             // MouseDown
             action = action.get("D");
@@ -1463,7 +1463,7 @@ class Catalog {
       }
     }
 
-    if (isDict(action)) {
+    if (action instanceof Dict) {
       const actionType = action.get("S");
       if (!isName(actionType)) {
         warn("parseDestDictionary: Invalid type in Action dictionary.");
@@ -1508,7 +1508,7 @@ class Catalog {
 
         case "GoToR":
           const urlDict = action.get("F");
-          if (isDict(urlDict)) {
+          if (urlDict instanceof Dict) {
             // We assume that we found a FileSpec dictionary
             // and fetch the URL without checking any further.
             url = urlDict.get("F") || null;

src/core/ccitt_stream.js

@@ -13,9 +13,9 @@
  * limitations under the License.
  */
 
-import { Dict, isDict } from "./primitives.js";
 import { CCITTFaxDecoder } from "./ccitt.js";
 import { DecodeStream } from "./decode_stream.js";
+import { Dict } from "./primitives.js";
 
 class CCITTFaxStream extends DecodeStream {
   constructor(str, maybeLength, params) {
@@ -24,7 +24,7 @@ class CCITTFaxStream extends DecodeStream {
     this.str = str;
     this.dict = str.dict;
 
-    if (!isDict(params)) {
+    if (!(params instanceof Dict)) {
       params = Dict.empty;
     }
 

src/core/colorspace.js

@@ -21,7 +21,7 @@ import {
   unreachable,
   warn,
 } from "../shared/util.js";
-import { isDict, isName, Name, Ref } from "./primitives.js";
+import { Dict, isName, Name, Ref } from "./primitives.js";
 import { BaseStream } from "./base_stream.js";
 import { MissingDataException } from "./core_utils.js";
 
@@ -392,9 +392,9 @@ class ColorSpace {
         case "Pattern":
           return new PatternCS(/* baseCS = */ null);
         default:
-          if (isDict(resources)) {
+          if (resources instanceof Dict) {
             const colorSpaces = resources.get("ColorSpace");
-            if (isDict(colorSpaces)) {
+            if (colorSpaces instanceof Dict) {
               const resourcesCS = colorSpaces.get(cs.name);
               if (resourcesCS) {
                 if (isName(resourcesCS)) {

src/core/crypto.js

@@ -24,7 +24,7 @@ import {
   utf8StringToString,
   warn,
 } from "../shared/util.js";
-import { isDict, isName, Name } from "./primitives.js";
+import { Dict, isName, Name } from "./primitives.js";
 import { DecryptStream } from "./decrypt_stream.js";
 
 class ARCFourCipher {
@@ -1713,7 +1713,7 @@ const CipherTransformFactory = (function CipherTransformFactoryClosure() {
           // Trying to find default handler -- it usually has Length.
           const cfDict = dict.get("CF");
           const streamCryptoName = dict.get("StmF");
-          if (isDict(cfDict) && isName(streamCryptoName)) {
+          if (cfDict instanceof Dict && isName(streamCryptoName)) {
             cfDict.suppressEncryption = true; // See comment below.
             const handlerDict = cfDict.get(streamCryptoName.name);
             keyLength = (handlerDict && handlerDict.get("Length")) || 128;
@@ -1838,7 +1838,7 @@ const CipherTransformFactory = (function CipherTransformFactoryClosure() {
 
       if (algorithm >= 4) {
         const cf = dict.get("CF");
-        if (isDict(cf)) {
+        if (cf instanceof Dict) {
           // The 'CF' dictionary itself should not be encrypted, and by setting
           // `suppressEncryption` we can prevent an infinite loop inside of
           // `XRef_fetchUncompressed` if the dictionary contains indirect

src/core/document.js

@@ -44,7 +44,7 @@ import {
   XRefEntryException,
   XRefParseException,
 } from "./core_utils.js";
-import { Dict, isDict, isName, Name, Ref } from "./primitives.js";
+import { Dict, isName, Name, Ref } from "./primitives.js";
 import { getXfaFontDict, getXfaFontName } from "./xfa_fonts.js";
 import { NullStream, Stream } from "./stream.js";
 import { AnnotationFactory } from "./annotation.js";
@@ -120,7 +120,7 @@ class Page {
     if (!Array.isArray(value)) {
       return value;
     }
-    if (value.length === 1 || !isDict(value[0])) {
+    if (value.length === 1 || !(value[0] instanceof Dict)) {
       return value[0];
     }
     return Dict.merge({ xref: this.xref, dictArray: value });
@@ -1175,7 +1175,7 @@ class PDFDocument {
       info("The document information dictionary is invalid.");
     }
 
-    if (isDict(infoDict)) {
+    if (infoDict instanceof Dict) {
       // Fill the document info with valid entries from the specification,
       // as well as any existing well-formed custom entries.
       for (const key of infoDict.getKeys()) {

src/core/evaluator.js

@@ -35,16 +35,7 @@ import {
   warn,
 } from "../shared/util.js";
 import { CMapFactory, IdentityCMap } from "./cmap.js";
-import {
+import { Cmd, Dict, EOF, isName, Name, Ref, RefSet } from "./primitives.js";
-  Cmd,
-  Dict,
-  EOF,
-  isDict,
-  isName,
-  Name,
-  Ref,
-  RefSet,
-} from "./primitives.js";
 import { ErrorFont, Font } from "./fonts.js";
 import { FontFlags, getFontType } from "./fonts_utils.js";
 import {
@@ -1042,7 +1033,7 @@ class PartialEvaluator {
             gStateObj.push([key, false]);
             break;
           }
-          if (isDict(value)) {
+          if (value instanceof Dict) {
             isSimpleGState = false;
 
             promise = promise.then(() => {
@@ -1162,7 +1153,7 @@ class PartialEvaluator {
     }
 
     font = xref.fetchIfRef(fontRef);
-    if (!isDict(font)) {
+    if (!(font instanceof Dict)) {
       return errorFont();
     }
 
@@ -1190,7 +1181,7 @@ class PartialEvaluator {
       fontID = `f${fontRef.toString()}`;
     }
 
-    if (hash && isDict(descriptor)) {
+    if (hash && descriptor instanceof Dict) {
       if (!descriptor.fontAliases) {
         descriptor.fontAliases = Object.create(null);
       }
@@ -1493,7 +1484,7 @@ class PartialEvaluator {
     if (isName(contentProperties)) {
       const properties = resources.get("Properties");
       optionalContent = properties.get(contentProperties.name);
-    } else if (isDict(contentProperties)) {
+    } else if (contentProperties instanceof Dict) {
       optionalContent = contentProperties;
     } else {
       throw new FormatError("Optional content properties malformed.");
@@ -1521,7 +1512,7 @@ class PartialEvaluator {
       const optionalContentGroups = optionalContent.get("OCGs");
       if (
         Array.isArray(optionalContentGroups) ||
-        isDict(optionalContentGroups)
+        optionalContentGroups instanceof Dict
       ) {
         const groupIds = [];
         if (Array.isArray(optionalContentGroups)) {
@@ -3133,7 +3124,7 @@ class PartialEvaluator {
             if (includeMarkedContent) {
               flushTextContentItem();
               let mcid = null;
-              if (isDict(args[1])) {
+              if (args[1] instanceof Dict) {
                 mcid = args[1].get("MCID");
               }
               textContent.items.push({
@@ -3197,7 +3188,7 @@ class PartialEvaluator {
     if (properties.composite) {
       // CIDSystemInfo helps to match CID to glyphs
       const cidSystemInfo = dict.get("CIDSystemInfo");
-      if (isDict(cidSystemInfo)) {
+      if (cidSystemInfo instanceof Dict) {
         properties.cidSystemInfo = {
           registry: stringToPDFString(cidSystemInfo.get("Registry")),
           ordering: stringToPDFString(cidSystemInfo.get("Ordering")),
@@ -3222,7 +3213,7 @@ class PartialEvaluator {
     let encoding;
     if (dict.has("Encoding")) {
       encoding = dict.get("Encoding");
-      if (isDict(encoding)) {
+      if (encoding instanceof Dict) {
         baseEncodingName = encoding.get("BaseEncoding");
         baseEncodingName = isName(baseEncodingName)
           ? baseEncodingName.name
@@ -3784,7 +3775,7 @@ class PartialEvaluator {
         hash.update(encoding.name);
       } else if (encoding instanceof Ref) {
         hash.update(encoding.toString());
-      } else if (isDict(encoding)) {
+      } else if (encoding instanceof Dict) {
         for (const entry of encoding.getRawValues()) {
           if (isName(entry)) {
             hash.update(entry.name);

src/core/file_spec.js

@@ -15,7 +15,7 @@
 
 import { stringToPDFString, warn } from "../shared/util.js";
 import { BaseStream } from "./base_stream.js";
-import { isDict } from "./primitives.js";
+import { Dict } from "./primitives.js";
 
 function pickPlatformItem(dict) {
   // Look for the filename in this order:
@@ -43,7 +43,7 @@ function pickPlatformItem(dict) {
  */
 class FileSpec {
   constructor(root, xref) {
-    if (!root || !isDict(root)) {
+    if (!(root instanceof Dict)) {
       return;
     }
     this.xref = xref;

src/core/function.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { Dict, isDict, Ref } from "./primitives.js";
+import { Dict, Ref } from "./primitives.js";
 import {
   FormatError,
   info,
@@ -508,7 +508,7 @@ function isPDFFunction(v) {
   let fnDict;
   if (typeof v !== "object") {
     return false;
-  } else if (isDict(v)) {
+  } else if (v instanceof Dict) {
     fnDict = v;
   } else if (v instanceof BaseStream) {
     fnDict = v.dict;

src/core/jbig2_stream.js

@@ -15,7 +15,7 @@
 
 import { BaseStream } from "./base_stream.js";
 import { DecodeStream } from "./decode_stream.js";
-import { isDict } from "./primitives.js";
+import { Dict } from "./primitives.js";
 import { Jbig2Image } from "./jbig2.js";
 import { shadow } from "../shared/util.js";
 
@@ -50,7 +50,7 @@ class Jbig2Stream extends DecodeStream {
     const jbig2Image = new Jbig2Image();
 
     const chunks = [];
-    if (isDict(this.params)) {
+    if (this.params instanceof Dict) {
       const globalsStream = this.params.get("JBIG2Globals");
       if (globalsStream instanceof BaseStream) {
         const globals = globalsStream.getBytes();

src/core/jpeg_stream.js

@@ -14,7 +14,7 @@
  */
 
 import { DecodeStream } from "./decode_stream.js";
-import { isDict } from "./primitives.js";
+import { Dict } from "./primitives.js";
 import { JpegImage } from "./jpg.js";
 import { shadow } from "../shared/util.js";
 
@@ -81,7 +81,7 @@ class JpegStream extends DecodeStream {
       }
     }
     // Fetching the 'ColorTransform' entry, if it exists.
-    if (isDict(this.params)) {
+    if (this.params instanceof Dict) {
       const colorTransform = this.params.get("ColorTransform");
       if (Number.isInteger(colorTransform)) {
         jpegOptions.colorTransform = colorTransform;

src/core/name_number_tree.js

@@ -13,8 +13,8 @@
  * limitations under the License.
  */
 
+import { Dict, RefSet } from "./primitives.js";
 import { FormatError, unreachable, warn } from "../shared/util.js";
-import { isDict, RefSet } from "./primitives.js";
 
 /**
  * A NameTree/NumberTree is like a Dict but has some advantageous properties,
@@ -43,7 +43,7 @@ class NameOrNumberTree {
     const queue = [this.root];
     while (queue.length > 0) {
       const obj = xref.fetchIfRef(queue.shift());
-      if (!isDict(obj)) {
+      if (!(obj instanceof Dict)) {
         continue;
       }
       if (obj.has("Kids")) {

src/core/parser.js

@@ -22,16 +22,7 @@ import {
   StreamType,
   warn,
 } from "../shared/util.js";
-import {
+import { Cmd, Dict, EOF, isCmd, isName, Name, Ref } from "./primitives.js";
-  Cmd,
-  Dict,
-  EOF,
-  isCmd,
-  isDict,
-  isName,
-  Name,
-  Ref,
-} from "./primitives.js";
 import {
   isWhiteSpace,
   MissingDataException,
@@ -1401,7 +1392,7 @@ class Linearization {
         Number.isInteger(obj1) &&
         Number.isInteger(obj2) &&
         isCmd(obj3, "obj") &&
-        isDict(linDict) &&
+        linDict instanceof Dict &&
         isNum((obj = linDict.get("Linearized"))) &&
         obj > 0
       )

src/core/predictor_stream.js

@@ -14,14 +14,14 @@
  */
 
 import { DecodeStream } from "./decode_stream.js";
+import { Dict } from "./primitives.js";
 import { FormatError } from "../shared/util.js";
-import { isDict } from "./primitives.js";
 
 class PredictorStream extends DecodeStream {
   constructor(str, maybeLength, params) {
     super(maybeLength);
 
-    if (!isDict(params)) {
+    if (!(params instanceof Dict)) {
       return str; // no prediction
     }
     const predictor = (this.predictor = params.get("Predictor") || 1);

src/core/struct_tree.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { isDict, isName, Ref } from "./primitives.js";
+import { Dict, isName, Ref } from "./primitives.js";
 import { isString, stringToPDFString, warn } from "../shared/util.js";
 import { NumberTree } from "./name_number_tree.js";
 
@@ -38,7 +38,7 @@ class StructTreeRoot {
 
   readRoleMap() {
     const roleMapDict = this.dict.get("RoleMap");
-    if (!isDict(roleMapDict)) {
+    if (!(roleMapDict instanceof Dict)) {
       return;
     }
     roleMapDict.forEach((key, value) => {
@@ -112,7 +112,7 @@ class StructElementNode {
     let kidDict = null;
     if (kid instanceof Ref) {
       kidDict = this.dict.xref.fetch(kid);
-    } else if (isDict(kid)) {
+    } else if (kid instanceof Dict) {
       kidDict = kid;
     }
     if (!kidDict) {
@@ -256,7 +256,7 @@ class StructTreePage {
       return false;
     }
 
-    if (isDict(obj)) {
+    if (obj instanceof Dict) {
       if (obj.objId !== dict.objId) {
         return false;
       }

src/core/writer.js

@@ -14,7 +14,7 @@
  */
 
 import { bytesToString, escapeString, warn } from "../shared/util.js";
-import { Dict, isDict, isName, Name, Ref } from "./primitives.js";
+import { Dict, isName, Name, Ref } from "./primitives.js";
 import { escapePDFName, parseXFAPath } from "./core_utils.js";
 import { SimpleDOMNode, SimpleXMLParser } from "./xml_parser.js";
 import { BaseStream } from "./base_stream.js";
@@ -86,7 +86,7 @@ function writeValue(value, buffer, transform) {
     buffer.push(numberToString(value));
   } else if (typeof value === "boolean") {
     buffer.push(value.toString());
-  } else if (isDict(value)) {
+  } else if (value instanceof Dict) {
     writeDict(value, buffer, transform);
   } else if (value instanceof BaseStream) {
     writeStream(value, buffer, transform);

test/unit/primitives_spec.js

@@ -518,6 +518,8 @@ describe("primitives", function () {
   });
 
   describe("isDict", function () {
+    /* eslint-disable no-restricted-syntax */
+
     it("handles non-dictionaries", function () {
       const nonDict = {};
       expect(isDict(nonDict)).toEqual(false);
@@ -535,6 +537,8 @@ describe("primitives", function () {
       expect(isDict(dict, "Page")).toEqual(true);
       expect(isDict(dict, "Contents")).toEqual(false);
     });
+
+    /* eslint-enable no-restricted-syntax */
   });
 
   describe("isRefsEqual", function () {