Replace the remaining occurences of instanceof Array with Array.isArray()

*Follow-up to PRs 8864 and 8813.*

As explained in https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray, `instanceof Array` can have inconsistent behavior. To ensure that only `Array.isArray` is used, an ESLint plugin/rule is added to enforce this.

.eslintrc

@@ -5,7 +5,8 @@
   },
 
   "plugins": [
-    "mozilla"
+    "mozilla",
+    "unicorn",
   ],
 
   "env": {
@@ -25,6 +26,7 @@
     // Plugins
     "mozilla/avoid-removeChild": "error",
     "mozilla/use-includes-instead-of-indexOf": "error",
+    "unicorn/no-array-instanceof": "error",
 
     // Possible errors
     "for-direction": "error",

package-lock.json

@@ -1820,6 +1820,15 @@
         }
       }
     },
+    "clean-regexp": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/clean-regexp/-/clean-regexp-1.0.0.tgz",
+      "integrity": "sha1-jffHquUf02h06PjQW5GAvBGj/tc=",
+      "dev": true,
+      "requires": {
+        "escape-string-regexp": "^1.0.5"
+      }
+    },
     "cli-cursor": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/cli-cursor/-/cli-cursor-2.1.0.tgz",
@@ -2752,6 +2761,16 @@
         }
       }
     },
+    "eslint-ast-utils": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/eslint-ast-utils/-/eslint-ast-utils-1.1.0.tgz",
+      "integrity": "sha512-otzzTim2/1+lVrlH19EfQQJEhVJSu0zOb9ygb3iapN6UlyaDtyRq4b5U1FuW0v1lRa9Fp/GJyHkSwm6NqABgCA==",
+      "dev": true,
+      "requires": {
+        "lodash.get": "^4.4.2",
+        "lodash.zip": "^4.2.0"
+      }
+    },
     "eslint-plugin-mozilla": {
       "version": "0.14.0",
       "resolved": "https://registry.npmjs.org/eslint-plugin-mozilla/-/eslint-plugin-mozilla-0.14.0.tgz",
@@ -2769,6 +2788,22 @@
       "integrity": "sha512-JnwpoH8Sv4QOjrTDutENBHzSnyYtspdjtglYtqUtAHe6f6LLKqykJle+UwFPg23GGwt5hI3amS9CRDezW8GAww==",
       "dev": true
     },
+    "eslint-plugin-unicorn": {
+      "version": "4.0.3",
+      "resolved": "https://registry.npmjs.org/eslint-plugin-unicorn/-/eslint-plugin-unicorn-4.0.3.tgz",
+      "integrity": "sha512-F1JMyd42hx4qGhIaVdOSbDyhcxPgTy4BOzctTCkV+hqebPBUOAQn1f5AhMK2LTyiqCmKiTs8huAErbLBSWKoCQ==",
+      "dev": true,
+      "requires": {
+        "clean-regexp": "^1.0.0",
+        "eslint-ast-utils": "^1.0.0",
+        "import-modules": "^1.1.0",
+        "lodash.camelcase": "^4.1.1",
+        "lodash.kebabcase": "^4.0.1",
+        "lodash.snakecase": "^4.0.1",
+        "lodash.upperfirst": "^4.2.0",
+        "safe-regex": "^1.1.0"
+      }
+    },
     "eslint-scope": {
       "version": "3.7.1",
       "resolved": "https://registry.npmjs.org/eslint-scope/-/eslint-scope-3.7.1.tgz",
@@ -4615,6 +4650,12 @@
       "integrity": "sha512-Pgs951kaMm5GXP7MOvxERINe3gsaVjUWFm+UZPSq9xYriQAksyhg0csnS0KXSNRD5NmNdapXEpjxG49+AKh/ug==",
       "dev": true
     },
+    "import-modules": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/import-modules/-/import-modules-1.1.0.tgz",
+      "integrity": "sha1-dI23nFzEK7lwHvq0JPiU5yYA6dw=",
+      "dev": true
+    },
     "imurmurhash": {
       "version": "0.1.4",
       "resolved": "https://registry.npmjs.org/imurmurhash/-/imurmurhash-0.1.4.tgz",
@@ -5478,6 +5519,12 @@
       "integrity": "sha1-+6HEUkwZ7ppfgTa0YJ8BfPTe1pI=",
       "dev": true
     },
+    "lodash.camelcase": {
+      "version": "4.3.0",
+      "resolved": "https://registry.npmjs.org/lodash.camelcase/-/lodash.camelcase-4.3.0.tgz",
+      "integrity": "sha1-soqmKIorn8ZRA1x3EfZathkDMaY=",
+      "dev": true
+    },
     "lodash.clone": {
       "version": "4.5.0",
       "resolved": "https://registry.npmjs.org/lodash.clone/-/lodash.clone-4.5.0.tgz",
@@ -5493,6 +5540,12 @@
         "lodash._root": "^3.0.0"
       }
     },
+    "lodash.get": {
+      "version": "4.4.2",
+      "resolved": "https://registry.npmjs.org/lodash.get/-/lodash.get-4.4.2.tgz",
+      "integrity": "sha1-LRd/ZS+jHpObRDjVNBSZ36OCXpk=",
+      "dev": true
+    },
     "lodash.isarguments": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/lodash.isarguments/-/lodash.isarguments-3.1.0.tgz",
@@ -5505,6 +5558,12 @@
       "integrity": "sha1-eeTriMNqgSKvhvhEqpvNhRtfu1U=",
       "dev": true
     },
+    "lodash.kebabcase": {
+      "version": "4.1.1",
+      "resolved": "https://registry.npmjs.org/lodash.kebabcase/-/lodash.kebabcase-4.1.1.tgz",
+      "integrity": "sha1-hImxyw0p/4gZXM7KRI/21swpXDY=",
+      "dev": true
+    },
     "lodash.keys": {
       "version": "3.1.2",
       "resolved": "https://registry.npmjs.org/lodash.keys/-/lodash.keys-3.1.2.tgz",
@@ -5522,6 +5581,12 @@
       "integrity": "sha1-k2pOMJ7zMKdkXtQUWYbIWuWyCAU=",
       "dev": true
     },
+    "lodash.snakecase": {
+      "version": "4.1.1",
+      "resolved": "https://registry.npmjs.org/lodash.snakecase/-/lodash.snakecase-4.1.1.tgz",
+      "integrity": "sha1-OdcUo1NXFHg3rv1ktdy7Fr7Nj40=",
+      "dev": true
+    },
     "lodash.some": {
       "version": "4.6.0",
       "resolved": "https://registry.npmjs.org/lodash.some/-/lodash.some-4.6.0.tgz",
@@ -5555,6 +5620,18 @@
         "lodash.escape": "^3.0.0"
       }
     },
+    "lodash.upperfirst": {
+      "version": "4.3.1",
+      "resolved": "https://registry.npmjs.org/lodash.upperfirst/-/lodash.upperfirst-4.3.1.tgz",
+      "integrity": "sha1-E2Xt9DFIBIHvDRxolXpe2Z1J984=",
+      "dev": true
+    },
+    "lodash.zip": {
+      "version": "4.2.0",
+      "resolved": "https://registry.npmjs.org/lodash.zip/-/lodash.zip-4.2.0.tgz",
+      "integrity": "sha1-7GZi5IlkCO1KtsVCo5kLcswIACA=",
+      "dev": true
+    },
     "long": {
       "version": "3.2.0",
       "resolved": "https://registry.npmjs.org/long/-/long-3.2.0.tgz",

package.json

@@ -13,6 +13,7 @@
     "eslint": "^5.1.0",
     "eslint-plugin-mozilla": "^0.14.0",
     "eslint-plugin-no-unsanitized": "^3.0.2",
+    "eslint-plugin-unicorn": "^4.0.3",
     "fancy-log": "^1.3.2",
     "gulp": "^3.9.1",
     "gulp-postcss": "^7.0.1",

test/unit/api_spec.js

@@ -752,12 +752,12 @@ describe('api', function() {
       var promise = doc.getOutline();
       promise.then(function(outline) {
         // Two top level entries.
-        expect(outline instanceof Array).toEqual(true);
+        expect(Array.isArray(outline)).toEqual(true);
         expect(outline.length).toEqual(2);
         // Make sure some basic attributes are set.
         var outlineItem = outline[1];
         expect(outlineItem.title).toEqual('Chapter 1');
-        expect(outlineItem.dest instanceof Array).toEqual(true);
+        expect(Array.isArray(outlineItem.dest)).toEqual(true);
         expect(outlineItem.url).toEqual(null);
         expect(outlineItem.unsafeUrl).toBeUndefined();
         expect(outlineItem.newWindow).toBeUndefined();
@@ -778,7 +778,7 @@ describe('api', function() {
 
       loadingTask.promise.then(function (pdfDocument) {
         pdfDocument.getOutline().then(function (outline) {
-          expect(outline instanceof Array).toEqual(true);
+          expect(Array.isArray(outline)).toEqual(true);
           expect(outline.length).toEqual(5);
 
           var outlineItemTwo = outline[2];

web/base_viewer.js

@@ -499,7 +499,7 @@ class BaseViewer {
     }
     if (!labels) {
       this._pageLabels = null;
-    } else if (!(labels instanceof Array &&
+    } else if (!(Array.isArray(labels) &&
                  this.pdfDocument.numPages === labels.length)) {
       this._pageLabels = null;
       console.error(`${this._name}.setPageLabels: Invalid page labels.`);

web/pdf_history.js

@@ -164,7 +164,7 @@ class PDFHistory {
       return;
     }
     if ((namedDest && typeof namedDest !== 'string') ||
-        !(explicitDest instanceof Array) ||
+        !Array.isArray(explicitDest) ||
         !(Number.isInteger(pageNumber) &&
           pageNumber > 0 && pageNumber <= this.linkService.pagesCount)) {
       console.error('PDFHistory.push: Invalid parameters.');
@@ -567,7 +567,7 @@ function isDestArraysEqual(firstDest, secondDest) {
     if (typeof first !== typeof second) {
       return false;
     }
-    if (first instanceof Array || second instanceof Array) {
+    if (Array.isArray(first) || Array.isArray(second)) {
       return false;
     }
     if (first !== null && typeof first === 'object' && second !== null) {
@@ -584,7 +584,7 @@ function isDestArraysEqual(firstDest, secondDest) {
     return first === second || (Number.isNaN(first) && Number.isNaN(second));
   }
 
-  if (!(firstDest instanceof Array && secondDest instanceof Array)) {
+  if (!(Array.isArray(firstDest) && Array.isArray(secondDest))) {
     return false;
   }
   if (firstDest.length !== secondDest.length) {

web/pdf_link_service.js

@@ -162,7 +162,7 @@ class PDFLinkService {
         explicitDest: dest,
       });
     }).then((data) => {
-      if (!(data.explicitDest instanceof Array)) {
+      if (!Array.isArray(data.explicitDest)) {
         console.error(`PDFLinkService.navigateTo: "${data.explicitDest}" is` +
                       ` not a valid destination array, for dest="${dest}".`);
         return;
@@ -179,7 +179,7 @@ class PDFLinkService {
     if (typeof dest === 'string') {
       return this.getAnchorUrl('#' + escape(dest));
     }
-    if (dest instanceof Array) {
+    if (Array.isArray(dest)) {
       let str = JSON.stringify(dest);
       return this.getAnchorUrl('#' + escape(str));
     }
@@ -273,7 +273,7 @@ class PDFLinkService {
       try {
         dest = JSON.parse(dest);
 
-        if (!(dest instanceof Array)) {
+        if (!Array.isArray(dest)) {
           // Avoid incorrectly rejecting a valid named destination, such as
           // e.g. "4.3" or "true", because `JSON.parse` converted its type.
           dest = dest.toString();
@@ -368,7 +368,7 @@ class PDFLinkService {
 }
 
 function isValidExplicitDestination(dest) {
-  if (!(dest instanceof Array)) {
+  if (!Array.isArray(dest)) {
     return false;
   }
   let destLength = dest.length, allowNull = true;

web/pdf_thumbnail_viewer.js

@@ -208,7 +208,7 @@ class PDFThumbnailViewer {
     }
     if (!labels) {
       this._pageLabels = null;
-    } else if (!(labels instanceof Array &&
+    } else if (!(Array.isArray(labels) &&
                  this.pdfDocument.numPages === labels.length)) {
       this._pageLabels = null;
       console.error('PDFThumbnailViewer_setPageLabels: Invalid page labels.');