Enable the unicorn/prefer-at ESLint plugin rule (PR 15008 follow-up)

Please find additional information here:
 - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at
 - https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/prefer-at.md

.eslintrc

@@ -49,6 +49,7 @@
     "unicorn/no-new-buffer": "error",
     "unicorn/no-instanceof-array": "error",
     "unicorn/no-useless-spread": "error",
+    "unicorn/prefer-at": "error",
     "unicorn/prefer-date-now": "error",
     "unicorn/prefer-dom-node-remove": "error",
     "unicorn/prefer-string-starts-ends-with": "error",

external/.eslintrc

@@ -6,4 +6,8 @@
   "env": {
     "node": true,
   },
+
+  "rules": {
+    "unicorn/prefer-at": "off",
+  },
 }

src/core/catalog.js

@@ -1212,7 +1212,7 @@ class Catalog {
     }
 
     while (queue.length > 0) {
-      const queueItem = queue[queue.length - 1];
+      const queueItem = queue.at(-1);
       const { currentNode, posInKids } = queueItem;
 
       let kids = currentNode.getRaw("Kids");

src/core/crypto.js

@@ -1014,7 +1014,7 @@ class AESBaseCipher {
     let outputLength = 16 * result.length;
     if (finalize) {
       // undo a padding that is described in RFC 2898
-      const lastBlock = result[result.length - 1];
+      const lastBlock = result.at(-1);
       let psLen = lastBlock[15];
       if (psLen <= 16) {
         for (let i = 15, ii = 16 - psLen; i >= ii; --i) {
@@ -1284,7 +1284,7 @@ const PDF20 = (function PDF20Closure() {
     let k = calculateSHA256(input, 0, input.length).subarray(0, 32);
     let e = [0];
     let i = 0;
-    while (i < 64 || e[e.length - 1] > i - 32) {
+    while (i < 64 || e.at(-1) > i - 32) {
       const combinedLength = password.length + k.length + userBytes.length,
         combinedArray = new Uint8Array(combinedLength);
       let writeOffset = 0;

src/core/document.js

@@ -1045,7 +1045,7 @@ class PDFDocument {
     const pdfFonts = [];
     const initialState = {
       get font() {
-        return pdfFonts[pdfFonts.length - 1];
+        return pdfFonts.at(-1);
       },
       set font(font) {
         pdfFonts.push(font);

src/core/evaluator.js

@@ -3066,7 +3066,7 @@ class PartialEvaluator {
               }
             }
 
-            const item = elements[elements.length - 1];
+            const item = elements.at(-1);
             if (typeof item === "string") {
               showSpacedTextBuffer.push(item);
             }

src/core/font_renderer.js

@@ -278,7 +278,7 @@ function compileGlyf(code, cmds, font) {
     }
     const instructionLength = getUint16(code, i);
     i += 2 + instructionLength; // skipping the instructions
-    const numberOfPoints = endPtsOfContours[endPtsOfContours.length - 1] + 1;
+    const numberOfPoints = endPtsOfContours.at(-1) + 1;
     const points = [];
     while (points.length < numberOfPoints) {
       flags = code[i++];
@@ -329,15 +329,15 @@ function compileGlyf(code, cmds, font) {
       const contour = points.slice(startPoint, endPoint + 1);
       if (contour[0].flags & 1) {
         contour.push(contour[0]); // using start point at the contour end
-      } else if (contour[contour.length - 1].flags & 1) {
+      } else if (contour.at(-1).flags & 1) {
         // first is off-curve point, trying to use one from the end
-        contour.unshift(contour[contour.length - 1]);
+        contour.unshift(contour.at(-1));
       } else {
         // start and end are off-curve points, creating implicit one
         const p = {
           flags: 1,
-          x: (contour[0].x + contour[contour.length - 1].x) / 2,
-          y: (contour[0].y + contour[contour.length - 1].y) / 2,
+          x: (contour[0].x + contour.at(-1).x) / 2,
+          y: (contour[0].y + contour.at(-1).y) / 2,
         };
         contour.unshift(p);
         contour.push(p);

src/core/fonts.js

@@ -515,7 +515,7 @@ function getRanges(glyphs, numGlyphs) {
 
 function createCmapTable(glyphs, numGlyphs) {
   const ranges = getRanges(glyphs, numGlyphs);
-  const numTables = ranges[ranges.length - 1][1] > 0xffff ? 2 : 1;
+  const numTables = ranges.at(-1)[1] > 0xffff ? 2 : 1;
   let cmap =
     "\x00\x00" + // version
     string16(numTables) + // numTables
@@ -2291,7 +2291,7 @@ class Font {
           // CALL
           if (!inFDEF && !inELSE) {
             // collecting information about which functions are used
-            funcId = stack[stack.length - 1];
+            funcId = stack.at(-1);
             if (isNaN(funcId)) {
               info("TT: CALL empty stack (or invalid entry).");
             } else {
@@ -2374,7 +2374,7 @@ class Font {
         } else if (op === 0x1c) {
           // JMPR
           if (!inFDEF && !inELSE) {
-            const offset = stack[stack.length - 1];
+            const offset = stack.at(-1);
             // only jumping forward to prevent infinite loop
             if (offset > 0) {
               i += offset - 1;

src/core/function.js

@@ -1166,7 +1166,7 @@ const PostScriptCompiler = (function PostScriptCompilerClosure() {
               i += 6;
               break;
             }
-            ast1 = stack[stack.length - 1];
+            ast1 = stack.at(-1);
             if (ast1.type === "literal" || ast1.type === "var") {
               // we don't have to save into intermediate variable a literal or
               // variable.

src/core/operator_list.js

@@ -27,7 +27,7 @@ function addState(parentState, pattern, checkFn, iterateFn, processFn) {
     const item = pattern[i];
     state = state[item] || (state[item] = []);
   }
-  state[pattern[pattern.length - 1]] = {
+  state[pattern.at(-1)] = {
     checkFn,
     iterateFn,
     processFn,

src/core/pattern.js

@@ -206,7 +206,7 @@ class RadialAxialShading extends BaseShading {
     }
     if (!extendEnd) {
       // Same idea as above in extendStart but for the end.
-      colorStops[colorStops.length - 1][0] -= BaseShading.SMALL_NUMBER;
+      colorStops.at(-1)[0] -= BaseShading.SMALL_NUMBER;
       colorStops.push([1, background]);
     }
 
@@ -501,11 +501,11 @@ class MeshShading extends BaseShading {
             verticesLeft = 3;
             break;
           case 1:
-            ps.push(ps[ps.length - 2], ps[ps.length - 1]);
+            ps.push(ps.at(-2), ps.at(-1));
             verticesLeft = 1;
             break;
           case 2:
-            ps.push(ps[ps.length - 3], ps[ps.length - 1]);
+            ps.push(ps.at(-3), ps.at(-1));
             verticesLeft = 1;
             break;
         }

src/core/type1_parser.js

@@ -228,7 +228,7 @@ const Type1CharString = (function Type1CharStringClosure() {
               // seac is like type 2's special endchar but it doesn't use the
               // first argument asb, so remove it.
               if (seacAnalysisEnabled) {
-                const asb = this.stack[this.stack.length - 5];
+                const asb = this.stack.at(-5);
                 this.seac = this.stack.splice(-4, 4);
                 this.seac[0] += this.lsb - asb;
                 error = this.executeCommand(0, COMMAND_MAP.endchar);

src/core/writer.js

@@ -249,7 +249,7 @@ function incrementalUpdate({
   const refForXrefTable = xrefInfo.newRef;
 
   let buffer, baseOffset;
-  const lastByte = originalData[originalData.length - 1];
+  const lastByte = originalData.at(-1);
   if (lastByte === /* \n */ 0x0a || lastByte === /* \r */ 0x0d) {
     buffer = [];
     baseOffset = originalData.length;

src/core/xfa/builder.js

@@ -182,7 +182,7 @@ class Builder {
     }
     const prefixStack = this._namespacePrefixes.get(prefix);
     if (prefixStack && prefixStack.length > 0) {
-      return prefixStack[prefixStack.length - 1];
+      return prefixStack.at(-1);
     }
 
     warn(`Unknown namespace prefix: ${prefix}.`);

src/core/xfa/data.js

@@ -32,7 +32,7 @@ class DataHandler {
     const stack = [[-1, this.data[$getChildren]()]];
 
     while (stack.length > 0) {
-      const last = stack[stack.length - 1];
+      const last = stack.at(-1);
       const [i, children] = last;
       if (i + 1 === children.length) {
         stack.pop();

src/core/xfa/formcalc_parser.js

@@ -354,7 +354,7 @@ class SimpleExprParser {
           return [tok, this.getNode()];
         case TOKEN.leftParen:
           if (this.last === OPERAND) {
-            const lastOperand = this.operands[this.operands.length - 1];
+            const lastOperand = this.operands.at(-1);
             if (!(lastOperand instanceof AstIdentifier)) {
               return [tok, this.getNode()];
             }
@@ -525,7 +525,7 @@ class SimpleExprParser {
 
   flushWithOperator(op) {
     while (true) {
-      const top = this.operators[this.operators.length - 1];
+      const top = this.operators.at(-1);
       if (top) {
         if (top.id >= 0 && SimpleExprParser.checkPrecedence(top, op)) {
           this.operators.pop();

src/core/xfa/html_utils.js

@@ -562,7 +562,7 @@ function isPrintOnly(node) {
 
 function getCurrentPara(node) {
   const stack = node[$getTemplateRoot]()[$extra].paraStack;
-  return stack.length ? stack[stack.length - 1] : null;
+  return stack.length ? stack.at(-1) : null;
 }
 
 function setPara(node, nodeStyle, value) {

src/core/xfa/som.js

@@ -100,7 +100,7 @@ function parseExpression(expr, dotDotAllowed, noExpr = true) {
         warn("XFA - Invalid index in SOM expression");
         return null;
       }
-      parsed[parsed.length - 1].index = parseIndex(match[0]);
+      parsed.at(-1).index = parseIndex(match[0]);
       pos += match[0].length + 1;
       continue;
     }

src/core/xfa/template.js

@@ -910,7 +910,7 @@ class Border extends XFAObject {
     if (!this[$extra]) {
       const edges = this.edge.children.slice();
       if (edges.length < 4) {
-        const defaultEdge = edges[edges.length - 1] || new Edge({});
+        const defaultEdge = edges.at(-1) || new Edge({});
         for (let i = edges.length; i < 4; i++) {
           edges.push(defaultEdge);
         }
@@ -950,7 +950,7 @@ class Border extends XFAObject {
     if (this.corner.children.some(node => node.radius !== 0)) {
       const cornerStyles = this.corner.children.map(node => node[$toStyle]());
       if (cornerStyles.length === 2 || cornerStyles.length === 3) {
-        const last = cornerStyles[cornerStyles.length - 1];
+        const last = cornerStyles.at(-1);
         for (let i = cornerStyles.length; i < 4; i++) {
           cornerStyles.push(last);
         }

src/core/xfa/text.js

@@ -102,7 +102,7 @@ class FontSelector {
   }
 
   pushData(xfaFont, margin, lineHeight) {
-    const lastFont = this.stack[this.stack.length - 1];
+    const lastFont = this.stack.at(-1);
     for (const name of [
       "typeface",
       "posture",
@@ -139,7 +139,7 @@ class FontSelector {
   }
 
   topFont() {
-    return this.stack[this.stack.length - 1];
+    return this.stack.at(-1);
   }
 }
 

src/core/xfa/xhtml.js

@@ -500,7 +500,7 @@ class P extends XhtmlObject {
 
   [$text]() {
     const siblings = this[$getParent]()[$getChildren]();
-    if (siblings[siblings.length - 1] === this) {
+    if (siblings.at(-1) === this) {
       return super[$text]();
     }
     return super[$text]() + "\n";

src/core/xfa_fonts.js

@@ -284,10 +284,7 @@ function getXfaFontDict(name) {
   dict.set("CIDToGIDMap", Name.get("Identity"));
   dict.set("W", widths);
   dict.set("FirstChar", widths[0]);
-  dict.set(
-    "LastChar",
-    widths[widths.length - 2] + widths[widths.length - 1].length - 1
-  );
+  dict.set("LastChar", widths.at(-2) + widths.at(-1).length - 1);
   const descriptor = new Dict(null);
   dict.set("FontDescriptor", descriptor);
   const systemInfo = new Dict(null);

src/core/xml_parser.js

@@ -494,7 +494,7 @@ class SimpleXMLParser extends XMLParserBase {
 
   onEndElement(name) {
     this._currentFragment = this._stack.pop() || [];
-    const lastElement = this._currentFragment[this._currentFragment.length - 1];
+    const lastElement = this._currentFragment.at(-1);
     if (!lastElement) {
       return null;
     }

src/display/editor/fit_curve/fit_curve.js

@@ -257,7 +257,7 @@ function generateBezier(points, parameters, leftTangent, rightTangent) {
     ux;
 
   const firstPoint = points[0];
-  const lastPoint = points[points.length - 1];
+  const lastPoint = points.at(-1);
 
   // Bezier curve ctl pts
   const bezCurve = [firstPoint, null, null, lastPoint];

src/display/svg.js

@@ -389,7 +389,7 @@ if (
       if (opListElement.fn === "save") {
         opTree.push({ fnId: 92, fn: "group", items: [] });
         tmp.push(opTree);
-        opTree = opTree[opTree.length - 1].items;
+        opTree = opTree.at(-1).items;
         continue;
       }
 

src/display/text_layer.js

@@ -488,7 +488,7 @@ function expandBoundsLTR(width, bounds) {
         affectedBoundary.x2 > boundary.x2 ? affectedBoundary : boundary;
       if (lastBoundary === useBoundary) {
         // Merging with previous.
-        changedHorizon[changedHorizon.length - 1].end = horizonPart.end;
+        changedHorizon.at(-1).end = horizonPart.end;
       } else {
         changedHorizon.push({
           start: horizonPart.start,
@@ -507,7 +507,7 @@ function expandBoundsLTR(width, bounds) {
       });
     }
     if (boundary.y2 < horizon[j].end) {
-      changedHorizon[changedHorizon.length - 1].end = boundary.y2;
+      changedHorizon.at(-1).end = boundary.y2;
       changedHorizon.push({
         start: boundary.y2,
         end: horizon[j].end,

src/display/xfa_layer.js

@@ -185,13 +185,13 @@ class XfaLayer {
     const textDivs = [];
 
     while (stack.length > 0) {
-      const [parent, i, html] = stack[stack.length - 1];
+      const [parent, i, html] = stack.at(-1);
       if (i + 1 === parent.children.length) {
         stack.pop();
         continue;
       }
 
-      const child = parent.children[++stack[stack.length - 1][1]];
+      const child = parent.children[++stack.at(-1)[1]];
       if (child === null) {
         continue;
       }

src/shared/compatibility.js

@@ -88,6 +88,14 @@ if (
     require("core-js/es/array/at.js");
   })();
 
+  // Support: Firefox<90, Chrome<92, Safari<15.4, Node.js<16.6.0
+  (function checkTypedArrayAt() {
+    if (Uint8Array.prototype.at) {
+      return;
+    }
+    require("core-js/es/typed-array/at.js");
+  })();
+
   // Support: Firefox<94, Chrome<98, Safari<15.4, Node.js<17.0.0
   (function checkStructuredClone() {
     if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("IMAGE_DECODERS")) {

test/resources/reftest-analyzer.js

@@ -229,7 +229,7 @@ window.onload = function () {
         /^ {2}IMAGE[^:]*\((\d+\.?\d*)x(\d+\.?\d*)x(\d+\.?\d*)\): (.*)$/
       );
       if (match) {
-        const item = gTestItems[gTestItems.length - 1];
+        const item = gTestItems.at(-1);
         item.images.push({
           width: parseFloat(match[1]),
           height: parseFloat(match[2]),

test/test.js

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint-disable no-var */
+/* eslint-disable no-var, unicorn/prefer-at */
 
 "use strict";
 

test/unit/ui_utils_spec.js

@@ -301,7 +301,7 @@ describe("ui_utils", function () {
           ids.add(view.id);
         }
       }
-      return { first: views[0], last: views[views.length - 1], views, ids };
+      return { first: views[0], last: views.at(-1), views, ids };
     }
 
     // This function takes a fixed layout of pages and compares the system under

web/ui_utils.js

@@ -588,7 +588,7 @@ function getVisibleElements({
   }
 
   const first = visible[0],
-    last = visible[visible.length - 1];
+    last = visible.at(-1);
 
   if (sortByVisibility) {
     visible.sort(function (a, b) {