refactor: use Array.prototype.at() to get last elements (#17949)

Makefile.js

@@ -340,7 +340,7 @@ function getFirstCommitOfFile(filePath) {
     let commits = execSilent(`git rev-list HEAD -- ${filePath}`);
 
     commits = splitCommandResultToLines(commits);
-    return commits[commits.length - 1].trim();
+    return commits.at(-1).trim();
 }
 
 /**

lib/linter/apply-disable-directives.js

@@ -171,7 +171,7 @@ function createCommentRemoval(directives, commentToken) {
     return {
         description: ruleIds.length <= 2
             ? ruleIds.join(" or ")
-            : `${ruleIds.slice(0, ruleIds.length - 1).join(", ")}, or ${ruleIds[ruleIds.length - 1]}`,
+            : `${ruleIds.slice(0, ruleIds.length - 1).join(", ")}, or ${ruleIds.at(-1)}`,
         fix: {
             range,
             text: " "
@@ -342,7 +342,7 @@ function applyDirectives(options) {
                 problem.suppressions = problem.suppressions.concat(suppressions);
             } else {
                 problem.suppressions = suppressions;
-                usedDisableDirectives.add(disableDirectivesForProblem[disableDirectivesForProblem.length - 1]);
+                usedDisableDirectives.add(disableDirectivesForProblem.at(-1));
             }
         }
 

lib/linter/code-path-analysis/code-path.js

@@ -196,7 +196,7 @@ class CodePath {
                 if (stack.length <= 1) {
                     broken = true;
                 } else {
-                    skippedSegment = stack[stack.length - 2][0];
+                    skippedSegment = stack.at(-2)[0];
                 }
             },
 
@@ -237,7 +237,7 @@ class CodePath {
              * Otherwise, we just read the value and sometimes modify the
              * record as we traverse.
              */
-            record = stack[stack.length - 1];
+            record = stack.at(-1);
             segment = record[0];
             index = record[1];
 

lib/linter/code-path-analysis/fork-context.js

@@ -207,7 +207,7 @@ class ForkContext {
     get head() {
         const list = this.segmentsList;
 
-        return list.length === 0 ? [] : list[list.length - 1];
+        return list.length === 0 ? [] : list.at(-1);
     }
 
     /**

lib/linter/report-translator.js

@@ -160,7 +160,7 @@ function mergeFixes(fixes, sourceCode) {
 
     const originalText = sourceCode.text;
     const start = fixes[0].range[0];
-    const end = fixes[fixes.length - 1].range[1];
+    const end = fixes.at(-1).range[1];
     let text = "";
     let lastPos = Number.MIN_SAFE_INTEGER;
 

lib/rules/array-bracket-spacing.js

@@ -199,7 +199,7 @@ module.exports = {
                     : sourceCode.getLastToken(node),
                 penultimate = sourceCode.getTokenBefore(last),
                 firstElement = node.elements[0],
-                lastElement = node.elements[node.elements.length - 1];
+                lastElement = node.elements.at(-1);
 
             const openingBracketMustBeSpaced =
                 options.objectsInArraysException && isObjectType(firstElement) ||

lib/rules/block-scoped-var.js

@@ -79,7 +79,7 @@ module.exports = {
             }
 
             // Defines a predicate to check whether or not a given reference is outside of valid scope.
-            const scopeRange = stack[stack.length - 1];
+            const scopeRange = stack.at(-1);
 
             /**
              * Check if a reference is out of scope

lib/rules/callback-return.js

@@ -147,7 +147,7 @@ module.exports = {
                 if (closestBlock.type === "BlockStatement") {
 
                     // find the last item in the block
-                    const lastItem = closestBlock.body[closestBlock.body.length - 1];
+                    const lastItem = closestBlock.body.at(-1);
 
                     // if the callback is the last thing in a block that might be ok
                     if (isCallbackExpression(node, lastItem)) {
@@ -168,7 +168,7 @@ module.exports = {
                     if (lastItem.type === "ReturnStatement") {
 
                         // but only if the callback is immediately before
-                        if (isCallbackExpression(node, closestBlock.body[closestBlock.body.length - 2])) {
+                        if (isCallbackExpression(node, closestBlock.body.at(-2))) {
                             return;
                         }
                     }

lib/rules/comma-dangle.js

@@ -154,7 +154,7 @@ module.exports = {
              * @returns {any} The last element
              */
             function last(array) {
-                return array[array.length - 1];
+                return array.at(-1);
             }
 
             switch (node.type) {

lib/rules/comma-style.js

@@ -218,7 +218,7 @@ module.exports = {
 
                         previousItemToken = tokenAfterItem
                             ? sourceCode.getTokenBefore(tokenAfterItem)
-                            : sourceCode.ast.tokens[sourceCode.ast.tokens.length - 1];
+                            : sourceCode.ast.tokens.at(-1);
                     } else {
                         previousItemToken = currentItemToken;
                     }

lib/rules/constructor-super.js

@@ -109,7 +109,7 @@ function isPossibleConstructor(node) {
             );
 
         case "SequenceExpression": {
-            const lastExpression = node.expressions[node.expressions.length - 1];
+            const lastExpression = node.expressions.at(-1);
 
             return isPossibleConstructor(lastExpression);
         }

lib/rules/default-case.js

@@ -54,7 +54,7 @@ module.exports = {
          * @returns {any} Last element
          */
         function last(collection) {
-            return collection[collection.length - 1];
+            return collection.at(-1);
         }
 
         //--------------------------------------------------------------------------

lib/rules/eol-last.js

@@ -45,7 +45,7 @@ module.exports = {
             Program: function checkBadEOF(node) {
                 const sourceCode = context.sourceCode,
                     src = sourceCode.getText(),
-                    lastLine = sourceCode.lines[sourceCode.lines.length - 1],
+                    lastLine = sourceCode.lines.at(-1),
                     location = {
                         column: lastLine.length,
                         line: sourceCode.lines.length
@@ -89,7 +89,7 @@ module.exports = {
                     });
                 } else if (mode === "never" && endsWithNewline) {
 
-                    const secondLastLine = sourceCode.lines[sourceCode.lines.length - 2];
+                    const secondLastLine = sourceCode.lines.at(-2);
 
                     // File is newline-terminated, but shouldn't be
                     context.report({

lib/rules/function-paren-newline.js

@@ -218,7 +218,7 @@ module.exports = {
                 case "FunctionExpression": {
                     const leftParen = sourceCode.getFirstToken(node, astUtils.isOpeningParenToken);
                     const rightParen = node.params.length
-                        ? sourceCode.getTokenAfter(node.params[node.params.length - 1], astUtils.isClosingParenToken)
+                        ? sourceCode.getTokenAfter(node.params.at(-1), astUtils.isClosingParenToken)
                         : sourceCode.getTokenAfter(leftParen);
 
                     return { leftParen, rightParen };
@@ -234,7 +234,7 @@ module.exports = {
                     }
 
                     const rightParen = node.params.length
-                        ? sourceCode.getTokenAfter(node.params[node.params.length - 1], astUtils.isClosingParenToken)
+                        ? sourceCode.getTokenAfter(node.params.at(-1), astUtils.isClosingParenToken)
                         : sourceCode.getTokenAfter(firstToken);
 
                     return {

lib/rules/indent-legacy.js

@@ -789,7 +789,7 @@ module.exports = {
             if (elements.length > 0) {
 
                 // Skip last block line check if last item in same line
-                if (elements[elements.length - 1].loc.end.line === node.loc.end.line) {
+                if (elements.at(-1).loc.end.line === node.loc.end.line) {
                     return;
                 }
             }
@@ -873,7 +873,7 @@ module.exports = {
          */
         function filterOutSameLineVars(node) {
             return node.declarations.reduce((finalCollection, elem) => {
-                const lastElem = finalCollection[finalCollection.length - 1];
+                const lastElem = finalCollection.at(-1);
 
                 if ((elem.loc.start.line !== node.loc.start.line && !lastElem) ||
                     (lastElem && lastElem.loc.start.line !== elem.loc.start.line)) {
@@ -892,7 +892,7 @@ module.exports = {
         function checkIndentInVariableDeclarations(node) {
             const elements = filterOutSameLineVars(node);
             const nodeIndent = getNodeIndent(node).goodChar;
-            const lastElement = elements[elements.length - 1];
+            const lastElement = elements.at(-1);
 
             const elementsIndent = nodeIndent + indentSize * options.VariableDeclarator[node.kind];
 
@@ -999,7 +999,7 @@ module.exports = {
             },
 
             VariableDeclaration(node) {
-                if (node.declarations[node.declarations.length - 1].loc.start.line > node.declarations[0].loc.start.line) {
+                if (node.declarations.at(-1).loc.start.line > node.declarations[0].loc.start.line) {
                     checkIndentInVariableDeclarations(node);
                 }
             },

lib/rules/indent.js

@@ -1077,7 +1077,7 @@ module.exports = {
             "ObjectExpression, ObjectPattern"(node) {
                 const openingCurly = sourceCode.getFirstToken(node);
                 const closingCurly = sourceCode.getTokenAfter(
-                    node.properties.length ? node.properties[node.properties.length - 1] : openingCurly,
+                    node.properties.length ? node.properties.at(-1) : openingCurly,
                     astUtils.isClosingBraceToken
                 );
 
@@ -1458,7 +1458,7 @@ module.exports = {
 
                 if (node.cases.length) {
                     sourceCode.getTokensBetween(
-                        node.cases[node.cases.length - 1],
+                        node.cases.at(-1),
                         closingCurly,
                         { includeComments: true, filter: astUtils.isCommentToken }
                     ).forEach(token => offsets.ignoreToken(token));
@@ -1509,7 +1509,7 @@ module.exports = {
                     variableIndent = DEFAULT_VARIABLE_INDENT;
                 }
 
-                if (node.declarations[node.declarations.length - 1].loc.start.line > node.loc.start.line) {
+                if (node.declarations.at(-1).loc.start.line > node.loc.start.line) {
 
                     /*
                      * VariableDeclarator indentation is a bit different from other forms of indentation, in that the

lib/rules/key-spacing.js

@@ -28,7 +28,7 @@ function containsLineTerminator(str) {
  * @returns {any} Last element of arr.
  */
 function last(arr) {
-    return arr[arr.length - 1];
+    return arr.at(-1);
 }
 
 /**

lib/rules/lines-around-directive.js

@@ -166,15 +166,15 @@ module.exports = {
                 reportError(firstDirective, "before", false);
             }
 
-            const lastDirective = directives[directives.length - 1];
+            const lastDirective = directives.at(-1);
             const statements = node.type === "Program" ? node.body : node.body.body;
 
             /*
              * Do not check after the last directive if the body only
              * contains a directive prologue and isn't followed by a comment to ensure
              * this rule behaves well with padded-blocks.
              */
-            if (lastDirective === statements[statements.length - 1] && !lastDirective.trailingComments) {
+            if (lastDirective === statements.at(-1) && !lastDirective.trailingComments) {
                 return;
             }
 

lib/rules/max-len.js

@@ -124,7 +124,7 @@ module.exports = {
         }
 
         // The options object must be the last option specified…
-        const options = Object.assign({}, context.options[context.options.length - 1]);
+        const options = Object.assign({}, context.options.at(-1));
 
         // …but max code length…
         if (typeof context.options[0] === "number") {
@@ -290,7 +290,7 @@ module.exports = {
                     if (isJSXEmptyExpressionInSingleLineContainer(containingNode)) {
 
                         // push a unique node only
-                        if (comments[comments.length - 1] !== containingNode.parent) {
+                        if (comments.at(-1) !== containingNode.parent) {
                             comments.push(containingNode.parent);
                         }
                     } else {

lib/rules/max-lines.js

@@ -148,7 +148,7 @@ module.exports = {
                  * If file ends with a linebreak, `sourceCode.lines` will have one extra empty line at the end.
                  * That isn't a real line, so we shouldn't count it.
                  */
-                if (lines.length > 1 && lines[lines.length - 1].text === "") {
+                if (lines.length > 1 && lines.at(-1).text === "") {
                     lines.pop();
                 }
 
@@ -174,7 +174,7 @@ module.exports = {
                         },
                         end: {
                             line: sourceCode.lines.length,
-                            column: sourceCode.lines[sourceCode.lines.length - 1].length
+                            column: sourceCode.lines.at(-1).length
                         }
                     };
 

lib/rules/multiline-comment-style.js

@@ -113,7 +113,7 @@ module.exports = {
 
             return /^\*\s*$/u.test(lines[0]) &&
                 lines.slice(1, -1).every(line => /^\s* /u.test(line)) &&
-                /^\s*$/u.test(lines[lines.length - 1]);
+                /^\s*$/u.test(lines.at(-1));
         }
 
         /**
@@ -272,11 +272,11 @@ module.exports = {
                     context.report({
                         loc: {
                             start: firstComment.loc.start,
-                            end: commentGroup[commentGroup.length - 1].loc.end
+                            end: commentGroup.at(-1).loc.end
                         },
                         messageId: "expectedBlock",
                         fix(fixer) {
-                            const range = [firstComment.range[0], commentGroup[commentGroup.length - 1].range[1]];
+                            const range = [firstComment.range[0], commentGroup.at(-1).range[1]];
 
                             return commentLines.some(value => value.startsWith("/"))
                                 ? null
@@ -301,7 +301,7 @@ module.exports = {
                         });
                     }
 
-                    if (!/^\s*$/u.test(lines[lines.length - 1])) {
+                    if (!/^\s*$/u.test(lines.at(-1))) {
                         context.report({
                             loc: {
                                 start: { line: firstComment.loc.end.line, column: firstComment.loc.end.column - 2 },
@@ -408,12 +408,12 @@ module.exports = {
                     context.report({
                         loc: {
                             start: firstComment.loc.start,
-                            end: commentGroup[commentGroup.length - 1].loc.end
+                            end: commentGroup.at(-1).loc.end
                         },
                         messageId: "expectedBlock",
                         fix(fixer) {
                             return fixer.replaceTextRange(
-                                [firstComment.range[0], commentGroup[commentGroup.length - 1].range[1]],
+                                [firstComment.range[0], commentGroup.at(-1).range[1]],
                                 convertToBlock(firstComment, commentLines)
                             );
                         }
@@ -459,7 +459,7 @@ module.exports = {
                             tokenBefore && tokenBefore.loc.end.line === comment.loc.start.line - 1 &&
                             tokenBefore === commentList[index - 1]
                         ) {
-                            commentGroups[commentGroups.length - 1].push(comment);
+                            commentGroups.at(-1).push(comment);
                         } else {
                             commentGroups.push([comment]);
                         }

lib/rules/newline-after-var.js

@@ -215,7 +215,7 @@ module.exports = {
                     fix(fixer) {
                         const linesBetween = sourceCode.getText().slice(lastToken.range[1], nextToken.range[0]).split(astUtils.LINEBREAK_MATCHER);
 
-                        return fixer.replaceTextRange([lastToken.range[1], nextToken.range[0]], `${linesBetween.slice(0, -1).join("")}\n${linesBetween[linesBetween.length - 1]}`);
+                        return fixer.replaceTextRange([lastToken.range[1], nextToken.range[0]], `${linesBetween.slice(0, -1).join("")}\n${linesBetween.at(-1)}`);
                     }
                 });
             }

lib/rules/newline-before-return.js

@@ -166,7 +166,7 @@ module.exports = {
          */
         function canFix(node) {
             const leadingComments = sourceCode.getCommentsBefore(node);
-            const lastLeadingComment = leadingComments[leadingComments.length - 1];
+            const lastLeadingComment = leadingComments.at(-1);
             const tokenBefore = sourceCode.getTokenBefore(node);
 
             if (leadingComments.length === 0) {