Use Map.prototype.getOrInsertComputed() more in the code-base

src/core/chunked_stream.js

@@ -346,13 +346,13 @@ class ChunkedStreamManager {
 
     const chunksToRequest = [];
     for (const chunk of chunksNeeded) {
-      let requestIds = this._requestsByChunk.get(chunk);
-      if (!requestIds) {
-        requestIds = [];
-        this._requestsByChunk.set(chunk, requestIds);
-
-        chunksToRequest.push(chunk);
-      }
+      const requestIds = this._requestsByChunk.getOrInsertComputed(
+        chunk,
+        () => {
+          chunksToRequest.push(chunk);
+          return [];
+        }
+      );
       requestIds.push(requestId);
     }
 

src/core/editor/pdf_editor.js

@@ -29,7 +29,7 @@ import {
 } from "../core_utils.js";
 import { Dict, isName, Name, Ref, RefSet, RefSetCache } from "../primitives.js";
 import { incrementalUpdate, writeValue } from "../writer.js";
-import { isArrayEqual, stringToBytes } from "../../shared/util.js";
+import { isArrayEqual, makeArr, stringToBytes } from "../../shared/util.js";
 import { NameTree, NumberTree } from "../name_number_tree.js";
 import { stringToAsciiOrUTF16BE, stringToPDFString } from "../string_utils.js";
 import { AnnotationFactory } from "../annotation.js";
@@ -510,20 +510,15 @@ class PDFEditor {
     const bytes = this.#rawStreamBytes(stream);
     const key = this.#resourceStreamKey(dictStr, bytes);
 
-    let bucket = this.#resourceStreamCache.get(key);
-    if (bucket) {
-      // Same key only means "maybe equal": confirm with an exact comparison.
-      for (const entry of bucket) {
-        if (
-          entry.dictStr === dictStr &&
-          isArrayEqual(this.#rawStreamBytes(entry.stream), bytes)
-        ) {
-          return entry.ref;
-        }
+    const bucket = this.#resourceStreamCache.getOrInsertComputed(key, makeArr);
+    // Same key only means "maybe equal": confirm with an exact comparison.
+    for (const entry of bucket) {
+      if (
+        entry.dictStr === dictStr &&
+        isArrayEqual(this.#rawStreamBytes(entry.stream), bytes)
+      ) {
+        return entry.ref;
       }
-    } else {
-      bucket = [];
-      this.#resourceStreamCache.set(key, bucket);
     }
     const ref = this.newRef;
     this.xref[ref.num] = stream;

src/core/primitives.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { assert, shadow, unreachable } from "../shared/util.js";
+import { assert, makeArr, shadow, unreachable } from "../shared/util.js";
 
 const CIRCULAR_REF = Symbol("CIRCULAR_REF");
 const EOF = Symbol("EOF");
@@ -242,11 +242,9 @@ class Dict {
         continue;
       }
       for (const [key, value] of dict.getRawEntries()) {
-        let property = properties.get(key);
-        if (property === undefined) {
-          property = [];
-          properties.set(key, property);
-        } else if (!mergeSubDicts || !(value instanceof Dict)) {
+        const property = properties.getOrInsertComputed(key, makeArr);
+
+        if (property.length && !(mergeSubDicts && value instanceof Dict)) {
           // Ignore additional entries, if either:
           //  - This is a "shallow" merge, where only the first element matters.
           //  - The value is *not* a `Dict`, since other types cannot be merged.

src/display/annotation_storage.js

@@ -241,9 +241,10 @@ class AnnotationStorage {
         continue;
       }
       const { type } = editorStats;
-      if (!typeToEditor.has(type)) {
-        typeToEditor.set(type, Object.getPrototypeOf(value).constructor);
-      }
+      typeToEditor.getOrInsertComputed(
+        type,
+        () => Object.getPrototypeOf(value).constructor
+      );
       stats ||= Object.create(null);
       const map = (stats[type] ||= new Map());
       for (const [key, val] of Object.entries(editorStats)) {

src/display/canvas.js

@@ -23,6 +23,7 @@ import {
   FONT_IDENTITY_MATRIX,
   ImageKind,
   info,
+  makeArr,
   makeMap,
   OPS,
   shadow,
@@ -1507,11 +1508,10 @@ class CanvasGraphics {
     }
     let knockoutFilter = "none";
     if (needsAlphaScaling && this.#knockoutFilterCache instanceof Map) {
-      knockoutFilter = this.#knockoutFilterCache.get(alpha);
-      if (!knockoutFilter) {
-        knockoutFilter = this.filterFactory.addKnockoutFilter(alpha);
-        this.#knockoutFilterCache.set(alpha, knockoutFilter);
-      }
+      knockoutFilter = this.#knockoutFilterCache.getOrInsertComputed(
+        alpha,
+        () => this.filterFactory.addKnockoutFilter(alpha)
+      );
     }
 
     if (!needsAlphaScaling || knockoutFilter !== "none") {
@@ -3682,11 +3682,10 @@ class CanvasGraphics {
         );
         const { canvas, context } = this.annotationCanvas;
         if (canvasName) {
-          let canvases = this.annotationCanvasMap.get(id);
-          if (!canvases) {
-            canvases = [];
-            this.annotationCanvasMap.set(id, canvases);
-          }
+          const canvases = this.annotationCanvasMap.getOrInsertComputed(
+            id,
+            makeArr
+          );
           canvas.setAttribute("data-canvas-name", canvasName);
           // Replace any same-named canvas from a previous render so stale
           // low-resolution canvases don't pile up across zooms.

src/display/editor/tools.js

@@ -23,6 +23,7 @@ import {
   AnnotationEditorType,
   FeatureTest,
   getUuid,
+  makeArr,
   shadow,
   SVG_NS,
   Util,
@@ -550,7 +551,7 @@ class KeyboardManager {
           continue;
         }
         this.callbacks
-          .getOrInsertComputed(keyName, () => [])
+          .getOrInsertComputed(keyName, makeArr)
           .push({ callback, options, modifiers });
       }
     }

web/debugger.mjs

@@ -459,11 +459,9 @@ class Stepper {
     const dependents = new Map();
     for (const [dependentIdx, { dependencies: ownDependencies }] of metadata) {
       for (const dependencyIdx of ownDependencies) {
-        let ownDependents = dependents.get(dependencyIdx);
-        if (!ownDependents) {
-          dependents.set(dependencyIdx, (ownDependents = new Set()));
-        }
-        ownDependents.add(dependentIdx);
+        dependents
+          .getOrInsertComputed(dependencyIdx, () => new Set())
+          .add(dependentIdx);
       }
     }