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

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";