Replace globalScope with the standard globalThis property instead

Please see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/globalThis and note that most (reasonably) modern browsers have supported this for a while now, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/globalThis#Browser_compatibility

Since ESLint doesn't support this new global yet, it was added to the `globals` list in the top-level configuration file to prevent issues.

Finally, for older browsers a polyfill was added in `ssrc/shared/compatibility.js`.

.eslintrc

@@ -19,6 +19,7 @@
   },
 
   "globals": {
+    "globalThis": false,
     "PDFJSDev": false,
     "exports": false,
     "SystemJS": false,

src/display/api.js

@@ -33,7 +33,6 @@ import {
 import { FontFaceObject, FontLoader } from './font_loader';
 import { apiCompatibilityParams } from './api_compatibility';
 import { CanvasGraphics } from './canvas';
-import { globalScope } from '../shared/global_scope';
 import { GlobalWorkerOptions } from './worker_options';
 import { MessageHandler } from '../shared/message_handler';
 import { Metadata } from './metadata';
@@ -2103,11 +2102,11 @@ class WorkerTransport {
           }
 
           let fontRegistry = null;
-          if (params.pdfBug && globalScope.FontInspector &&
-              globalScope.FontInspector.enabled) {
+          if (params.pdfBug && globalThis.FontInspector &&
+              globalThis.FontInspector.enabled) {
             fontRegistry = {
               registerFont(font, url) {
-                globalScope['FontInspector'].fontAdded(font, url);
+                globalThis.FontInspector.fontAdded(font, url);
               },
             };
           }
@@ -2608,9 +2607,9 @@ const InternalRenderTask = (function InternalRenderTaskClosure() {
         canvasInRendering.add(this._canvas);
       }
 
-      if (this._pdfBug && globalScope.StepperManager &&
-          globalScope.StepperManager.enabled) {
-        this.stepper = globalScope.StepperManager.create(this.pageNumber - 1);
+      if (this._pdfBug && globalThis.StepperManager &&
+          globalThis.StepperManager.enabled) {
+        this.stepper = globalThis.StepperManager.create(this.pageNumber - 1);
         this.stepper.init(this.operatorList);
         this.stepper.nextBreakPoint = this.stepper.getNextBreakPoint();
       }

src/display/text_layer.js

@@ -14,7 +14,6 @@
  */
 
 import { AbortException, createPromiseCapability, Util } from '../shared/util';
-import { globalScope } from '../shared/global_scope';
 
 /**
  * Text layer render parameters.
@@ -469,8 +468,8 @@ var renderTextLayer = (function renderTextLayerClosure() {
     this._textDivs = textDivs || [];
     this._textContentItemsStr = textContentItemsStr || [];
     this._enhanceTextSelection = !!enhanceTextSelection;
-    this._fontInspectorEnabled = !!(globalScope.FontInspector &&
-                                    globalScope.FontInspector.enabled);
+    this._fontInspectorEnabled = !!(globalThis.FontInspector &&
+                                    globalThis.FontInspector.enabled);
 
     this._reader = null;
     this._layoutTextLastFontSize = null;

src/shared/compatibility.js

@@ -14,13 +14,18 @@
  */
 /* eslint no-var: error */
 
-const { globalScope, } = require('./global_scope');
-
 // Skip compatibility checks for modern builds and if we already ran the module.
 if ((typeof PDFJSDev === 'undefined' || !PDFJSDev.test('SKIP_BABEL')) &&
-    !globalScope._pdfjsCompatibilityChecked) {
+    (typeof globalThis === 'undefined' ||
+     !globalThis._pdfjsCompatibilityChecked)) {
 
-globalScope._pdfjsCompatibilityChecked = true;
+// Provides support for globalThis in legacy browsers.
+// Support: IE11/Edge, Opera
+if (typeof globalThis === 'undefined' || globalThis.Math !== Math) {
+  // eslint-disable-next-line no-global-assign
+  globalThis = require('core-js/es/global-this');
+}
+globalThis._pdfjsCompatibilityChecked = true;
 
 const { isNodeJS, } = require('./is_node');
 
@@ -31,10 +36,10 @@ const isIE = /Trident/.test(userAgent);
 
 // Support: Node.js
 (function checkNodeBtoa() {
-  if (globalScope.btoa || !isNodeJS) {
+  if (globalThis.btoa || !isNodeJS) {
     return;
   }
-  globalScope.btoa = function(chars) {
+  globalThis.btoa = function(chars) {
     // eslint-disable-next-line no-undef
     return Buffer.from(chars, 'binary').toString('base64');
   };
@@ -42,10 +47,10 @@ const isIE = /Trident/.test(userAgent);
 
 // Support: Node.js
 (function checkNodeAtob() {
-  if (globalScope.atob || !isNodeJS) {
+  if (globalThis.atob || !isNodeJS) {
     return;
   }
-  globalScope.atob = function(input) {
+  globalThis.atob = function(input) {
     // eslint-disable-next-line no-undef
     return Buffer.from(input, 'base64').toString('binary');
   };
@@ -223,11 +228,11 @@ const isIE = /Trident/.test(userAgent);
     // need to be polyfilled for the IMAGE_DECODERS build target.
     return;
   }
-  if (globalScope.Promise && (globalScope.Promise.prototype &&
-                              globalScope.Promise.prototype.finally)) {
+  if (globalThis.Promise && (globalThis.Promise.prototype &&
+                             globalThis.Promise.prototype.finally)) {
     return;
   }
-  globalScope.Promise = require('core-js/es/promise/index');
+  globalThis.Promise = require('core-js/es/promise/index');
 })();
 
 // Support: IE
@@ -241,23 +246,23 @@ const isIE = /Trident/.test(userAgent);
     // The `URL` constructor is assumed to be available in the extension builds.
     return;
   }
-  globalScope.URL = require('core-js/web/url');
+  globalThis.URL = require('core-js/web/url');
 })();
 
 // Support: IE<11, Safari<8, Chrome<36
 (function checkWeakMap() {
-  if (globalScope.WeakMap) {
+  if (globalThis.WeakMap) {
     return;
   }
-  globalScope.WeakMap = require('core-js/es/weak-map/index');
+  globalThis.WeakMap = require('core-js/es/weak-map/index');
 })();
 
 // Support: IE11
 (function checkWeakSet() {
-  if (globalScope.WeakSet) {
+  if (globalThis.WeakSet) {
     return;
   }
-  globalScope.WeakSet = require('core-js/es/weak-set/index');
+  globalThis.WeakSet = require('core-js/es/weak-set/index');
 })();
 
 // Provides support for String.codePointAt in legacy browsers.
@@ -280,7 +285,7 @@ const isIE = /Trident/.test(userAgent);
 
 // Support: IE
 (function checkSymbol() {
-  if (globalScope.Symbol) {
+  if (globalThis.Symbol) {
     return;
   }
   require('core-js/es/symbol/index');

src/shared/global_scope.js

@@ -1,24 +0,0 @@
-/* Copyright 2017 Mozilla Foundation
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-const globalScope =
-  (typeof window !== 'undefined' && window.Math === Math) ? window :
-  // eslint-disable-next-line no-undef
-  (typeof global !== 'undefined' && global.Math === Math) ? global :
-  (typeof self !== 'undefined' && self.Math === Math) ? self : {};
-
-export {
-  globalScope,
-};