diff --git a/.eslintrc.json b/.eslintrc.json
index 2ea9622d72e9d..1711f8592ab18 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -2,7 +2,6 @@
     "parser": "@typescript-eslint/parser",
     "parserOptions": {
         "warnOnUnsupportedTypeScriptVersion": false,
-        "ecmaVersion": 6,
         "sourceType": "module"
     },
     "env": {
@@ -27,6 +26,7 @@
     "rules": {
         "@typescript-eslint/adjacent-overload-signatures": "error",
         "@typescript-eslint/array-type": "error",
+        "@typescript-eslint/no-array-constructor": "error",
 
         "brace-style": "off",
         "@typescript-eslint/brace-style": ["error", "stroustrup", { "allowSingleLine": true }],
@@ -62,12 +62,14 @@
         "@typescript-eslint/prefer-for-of": "error",
         "@typescript-eslint/prefer-function-type": "error",
         "@typescript-eslint/prefer-namespace-keyword": "error",
+        "@typescript-eslint/prefer-as-const": "error",
 
         "quotes": "off",
         "@typescript-eslint/quotes": ["error", "double", { "avoidEscape": true, "allowTemplateLiterals": true }],
 
         "semi": "off",
         "@typescript-eslint/semi": "error",
+        "@typescript-eslint/no-extra-semi": "error",
 
         "space-before-function-paren": "off",
         "@typescript-eslint/space-before-function-paren": ["error", {
@@ -80,6 +82,8 @@
         "@typescript-eslint/type-annotation-spacing": "error",
         "@typescript-eslint/unified-signatures": "error",
 
+        "@typescript-eslint/no-extra-non-null-assertion": "error",
+
         // scripts/eslint/rules
         "local/object-literal-surrounding-space": "error",
         "local/no-type-assertion-whitespace": "error",
@@ -143,6 +147,9 @@
         "quote-props": ["error", "consistent-as-needed"],
         "space-in-parens": "error",
         "unicode-bom": ["error", "never"],
-        "use-isnan": "error"
+        "use-isnan": "error",
+        "no-prototype-builtins": "error",
+        "no-self-assign": "error",
+        "no-dupe-else-if": "error"
     }
 }
diff --git a/scripts/word2md.ts b/scripts/word2md.ts
index ed0338617d8be..472699156bb8b 100644
--- a/scripts/word2md.ts
+++ b/scripts/word2md.ts
@@ -185,7 +185,7 @@ function convertDocumentToMarkdown(doc: Word.Document): string {
 
     function setProperties(target: any, properties: any) {
         for (const name in properties) {
-            if (properties.hasOwnProperty(name)) {
+            if (Object.prototype.hasOwnProperty.call(properties, name)) {
                 const value = properties[name];
                 if (typeof value === "object") {
                     setProperties(target[name], value);
diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 1e347f9d81e15..4c3eac092b45a 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -3044,7 +3044,7 @@ namespace ts {
                 return;
             }
             const rootExpr = getLeftmostAccessExpression(node.left);
-            if (isIdentifier(rootExpr) && lookupSymbolForName(container, rootExpr.escapedText)!?.flags & SymbolFlags.Alias) {
+            if (isIdentifier(rootExpr) && lookupSymbolForName(container, rootExpr.escapedText)?.flags! & SymbolFlags.Alias) {
                 return;
             }
             // Fix up parent pointers since we're going to use these nodes before we bind into them
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index f992dd0ea458f..afac9b5a1ae85 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9219,7 +9219,7 @@ namespace ts {
                 if (container && (container.kind === SyntaxKind.Constructor || isJSConstructor(container))) {
                     return container as ConstructorDeclaration;
                 }
-            };
+            }
         }
 
         /** Create a synthetic property access flow node after the last statement of the file */
@@ -29892,7 +29892,7 @@ namespace ts {
                     return !!s && getMinArgumentCount(s) >= 1 && isTypeAssignableTo(keyedType, getTypeAtPosition(s, 0));
                 }
                 return false;
-            };
+            }
 
             const suggestedMethod = isAssignmentTarget(expr) ? "set" : "get";
             if (!hasProp(suggestedMethod)) {
diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index 7ad3644970b6f..b3dcb04c777d9 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -3709,7 +3709,7 @@ namespace ts {
     export function convertCompilerOptionsForTelemetry(opts: CompilerOptions): CompilerOptions {
         const out: CompilerOptions = {};
         for (const key in opts) {
-            if (opts.hasOwnProperty(key)) {
+            if (hasProperty(opts, key)) {
                 const type = getOptionFromName(key);
                 if (type !== undefined) { // Ignore unknown options
                     out[key] = getOptionValueWithEmptyStrings(opts[key], type);
diff --git a/src/compiler/debug.ts b/src/compiler/debug.ts
index d6edd94b3dc49..70893ceb29bc1 100644
--- a/src/compiler/debug.ts
+++ b/src/compiler/debug.ts
@@ -279,7 +279,7 @@ namespace ts {
             if (typeof func !== "function") {
                 return "";
             }
-            else if (func.hasOwnProperty("name")) {
+            else if (hasProperty(func, "name")) {
                 return (func as any).name;
             }
             else {
@@ -625,7 +625,7 @@ namespace ts {
             ];
 
             for (const ctor of nodeConstructors) {
-                if (!ctor.prototype.hasOwnProperty("__debugKind")) {
+                if (!hasProperty(ctor, "__debugKind")) {
                     Object.defineProperties(ctor.prototype, {
                         // for use with vscode-js-debug's new customDescriptionGenerator in launch.json
                         __tsDebuggerDisplay: {
diff --git a/src/compiler/factory/nodeFactory.ts b/src/compiler/factory/nodeFactory.ts
index 9d7a2fce604d5..27b2b75e9c7f0 100644
--- a/src/compiler/factory/nodeFactory.ts
+++ b/src/compiler/factory/nodeFactory.ts
@@ -5639,7 +5639,7 @@ namespace ts {
             setOriginalNode(clone, node);
 
             for (const key in node) {
-                if (clone.hasOwnProperty(key) || !node.hasOwnProperty(key)) {
+                if (hasProperty(clone, key) || !hasProperty(node, key)) {
                     continue;
                 }
 
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 85f13a159ca04..91b94fc57c0e7 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -744,7 +744,7 @@ namespace ts {
         return visitNodes(cbNode, cbNodes, node.typeParameters) ||
             visitNodes(cbNode, cbNodes, node.parameters) ||
             visitNode(cbNode, node.type);
-    };
+    }
 
     function forEachChildInUnionOrIntersectionType<T>(node: UnionTypeNode | IntersectionTypeNode, cbNode: (node: Node) => T | undefined, cbNodes?: (nodes: NodeArray<Node>) => T | undefined): T | undefined {
         return visitNodes(cbNode, cbNodes, node.types);
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 412f307eae4bf..5b48d317db7df 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -503,7 +503,7 @@ namespace ts {
         /* @internal */ imports: SourceFile["imports"];
         /* @internal */ moduleAugmentations: SourceFile["moduleAugmentations"];
         impliedNodeFormat?: SourceFile["impliedNodeFormat"];
-    };
+    }
 
     /**
      * Calculates the resulting resolution mode for some reference in some file - this is generally the explicitly
diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index a54389fbb9474..1bb62f652241c 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -361,7 +361,7 @@ namespace ts {
 
     /* @internal */
     export function computeLineStarts(text: string): number[] {
-        const result: number[] = new Array();
+        const result: number[] = [];
         let pos = 0;
         let lineStart = 0;
         while (pos < text.length) {
diff --git a/src/compiler/tracing.ts b/src/compiler/tracing.ts
index 5c7037b7e5c53..54f378d61cc16 100644
--- a/src/compiler/tracing.ts
+++ b/src/compiler/tracing.ts
@@ -25,7 +25,7 @@ namespace ts { // eslint-disable-line local/one-namespace-per-file
         // The actual constraint is that JSON.stringify be able to serialize it without throwing.
         interface Args {
             [key: string]: string | number | boolean | null | undefined | Args | readonly (string | number | boolean | null | undefined | Args)[];
-        };
+        }
 
         /** Starts tracing for the given project. */
         export function startTracing(tracingMode: Mode, traceDir: string, configFilePath?: string) {
diff --git a/src/compiler/transformers/declarations.ts b/src/compiler/transformers/declarations.ts
index d64c14b2e0b2c..e453b77a3bff2 100644
--- a/src/compiler/transformers/declarations.ts
+++ b/src/compiler/transformers/declarations.ts
@@ -218,9 +218,9 @@ namespace ts {
         }
 
         function reportNonlocalAugmentation(containingFile: SourceFile, parentSymbol: Symbol, symbol: Symbol) {
-            const primaryDeclaration = parentSymbol.declarations?.find(d => getSourceFileOfNode(d) === containingFile)!;
+            const primaryDeclaration = parentSymbol.declarations?.find(d => getSourceFileOfNode(d) === containingFile);
             const augmentingDeclarations = filter(symbol.declarations, d => getSourceFileOfNode(d) !== containingFile);
-            if (augmentingDeclarations) {
+            if (primaryDeclaration && augmentingDeclarations) {
                 for (const augmentations of augmentingDeclarations) {
                     context.addDiagnostic(addRelatedInfo(
                         createDiagnosticForNode(augmentations, Diagnostics.Declaration_augments_declaration_in_another_file_This_cannot_be_serialized),
diff --git a/src/compiler/tsbuildPublic.ts b/src/compiler/tsbuildPublic.ts
index 0849c5921f29a..7c773f5bdc3c5 100644
--- a/src/compiler/tsbuildPublic.ts
+++ b/src/compiler/tsbuildPublic.ts
@@ -487,7 +487,7 @@ namespace ts {
         // TODO(rbuckton): Should be a `Set`, but that requires changing the code below that uses `mutateMapSkippingNewValues`
         const currentProjects = new Map(
             getBuildOrderFromAnyBuildOrder(buildOrder).map(
-                resolved => [toResolvedConfigFilePath(state, resolved), true as true])
+                resolved => [toResolvedConfigFilePath(state, resolved), true as const])
         );
 
         const noopOnDelete = { onDeleteValue: noop };
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 792c7d1f5cb3c..cdc0db9407b34 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -563,7 +563,7 @@ namespace ts {
 
     interface ScriptTargetFeatures {
         [key: string]: { [key: string]: string[] | undefined };
-    };
+    }
 
     export function getScriptTargetFeatures(): ScriptTargetFeatures {
         return {
@@ -5558,7 +5558,7 @@ namespace ts {
 
     export function isWatchSet(options: CompilerOptions) {
         // Firefox has Object.prototype.watch
-        return options.watch && options.hasOwnProperty("watch");
+        return options.watch && hasProperty(options, "watch");
     }
 
     export function closeFileWatcher(watcher: FileWatcher) {
diff --git a/src/compiler/utilitiesPublic.ts b/src/compiler/utilitiesPublic.ts
index c8b959eb8f87c..c6e083e9d7e1a 100644
--- a/src/compiler/utilitiesPublic.ts
+++ b/src/compiler/utilitiesPublic.ts
@@ -1121,7 +1121,7 @@ namespace ts {
 
     /* @internal */
     export function isNodeArray<T extends Node>(array: readonly T[]): array is NodeArray<T> {
-        return array.hasOwnProperty("pos") && array.hasOwnProperty("end");
+        return hasProperty(array, "pos") && hasProperty(array, "end");
     }
 
     // Literals
diff --git a/src/executeCommandLine/executeCommandLine.ts b/src/executeCommandLine/executeCommandLine.ts
index cb3ba0575a146..5a891ad05c580 100644
--- a/src/executeCommandLine/executeCommandLine.ts
+++ b/src/executeCommandLine/executeCommandLine.ts
@@ -431,7 +431,7 @@ namespace ts {
     function getHeader(sys: System, message: string) {
         const colors = createColors(sys);
         const header: string[] = [];
-        const terminalWidth = sys.getWidthOfTerminal?.() ?? 0;;
+        const terminalWidth = sys.getWidthOfTerminal?.() ?? 0;
         const tsIconLength = 5;
 
         const tsIconFirstLine = colors.blueBackground(padLeft("", tsIconLength));
diff --git a/src/harness/fourslashImpl.ts b/src/harness/fourslashImpl.ts
index 46d2bc242e772..72ceb827adf95 100644
--- a/src/harness/fourslashImpl.ts
+++ b/src/harness/fourslashImpl.ts
@@ -2737,7 +2737,7 @@ namespace FourSlash {
                 const identifier = this.classificationToIdentifier(a.classificationType as number);
                 const text = this.activeFile.content.slice(a.textSpan.start, a.textSpan.start + a.textSpan.length);
                 replacement.push(`    c2.semanticToken("${identifier}", "${text}"), `);
-            };
+            }
             replacement.push(");");
 
             throw new Error("You need to change the source code of fourslash test to use replaceWithSemanticClassifications");
diff --git a/src/harness/fourslashInterfaceImpl.ts b/src/harness/fourslashInterfaceImpl.ts
index 4112072d38835..52acb7d347eec 100644
--- a/src/harness/fourslashInterfaceImpl.ts
+++ b/src/harness/fourslashInterfaceImpl.ts
@@ -1900,11 +1900,11 @@ namespace FourSlashInterface {
     };
     export interface DiagnosticIgnoredInterpolations {
         template: string
-    };
+    }
     export type RenameLocationOptions = FourSlash.Range | { readonly range: FourSlash.Range, readonly prefixText?: string, readonly suffixText?: string };
     export interface RenameOptions {
         readonly findInStrings?: boolean;
         readonly findInComments?: boolean;
         readonly providePrefixAndSuffixTextForRename?: boolean;
-    };
+    }
 }
diff --git a/src/harness/harnessIO.ts b/src/harness/harnessIO.ts
index 2786498d41e1f..87148c13492a7 100644
--- a/src/harness/harnessIO.ts
+++ b/src/harness/harnessIO.ts
@@ -335,7 +335,7 @@ namespace Harness {
 
         export function setCompilerOptionsFromHarnessSetting(settings: TestCaseParser.CompilerSettings, options: ts.CompilerOptions & HarnessOptions): void {
             for (const name in settings) {
-                if (settings.hasOwnProperty(name)) {
+                if (ts.hasProperty(settings, name)) {
                     const value = settings[name];
                     if (value === undefined) {
                         throw new Error(`Cannot have undefined value for compiler option '${name}'.`);
@@ -1496,7 +1496,7 @@ namespace Harness {
 
     export function getConfigNameFromFileName(filename: string): "tsconfig.json" | "jsconfig.json" | undefined {
         const flc = ts.getBaseFileName(filename).toLowerCase();
-        return ts.find(["tsconfig.json" as "tsconfig.json", "jsconfig.json" as "jsconfig.json"], x => x === flc);
+        return ts.find(["tsconfig.json" as const, "jsconfig.json" as const], x => x === flc);
     }
 
     if (Error) (Error as any).stackTraceLimit = 100;
diff --git a/src/harness/harnessUtils.ts b/src/harness/harnessUtils.ts
index 97da7e0e3ec99..5ac968035346d 100644
--- a/src/harness/harnessUtils.ts
+++ b/src/harness/harnessUtils.ts
@@ -314,7 +314,7 @@ namespace Utils {
 
     function findChildName(parent: any, child: any) {
         for (const name in parent) {
-            if (parent.hasOwnProperty(name) && parent[name] === child) {
+            if (ts.hasProperty(parent, name) && parent[name] === child) {
                 return name;
             }
         }
diff --git a/src/harness/vfsUtil.ts b/src/harness/vfsUtil.ts
index 63a3d6963d55e..f102bb0ddb63a 100644
--- a/src/harness/vfsUtil.ts
+++ b/src/harness/vfsUtil.ts
@@ -916,7 +916,6 @@ namespace vfs {
                 if (this._shadowRoot) {
                     this._copyShadowLinks(this._shadowRoot._getRootLinks(), this._lazy.links);
                 }
-                this._lazy.links = this._lazy.links;
             }
             return this._lazy.links;
         }
@@ -1578,7 +1577,7 @@ namespace vfs {
             const entry = normalizeFileSetEntry(container[name]);
             const file = dirname ? vpath.combine(dirname, name) : name;
             // eslint-disable-next-line no-null/no-null
-            if (entry === null || entry === undefined || entry instanceof Unlink || entry instanceof Rmdir) {
+            if (entry === null || entry === undefined || entry instanceof Unlink) {
                 text += `//// [${file}] unlink\r\n`;
             }
             else if (entry instanceof Rmdir) {
diff --git a/src/loggedIO/loggedIO.ts b/src/loggedIO/loggedIO.ts
index 24b3f815f605e..6018ee1026e3d 100644
--- a/src/loggedIO/loggedIO.ts
+++ b/src/loggedIO/loggedIO.ts
@@ -94,7 +94,7 @@ namespace Playback { // eslint-disable-line local/one-namespace-per-file
     function memoize<T>(func: (s: string) => T): Memoized<T> {
         let lookup: { [s: string]: T } = {};
         const run: Memoized<T> = ((s: string) => {
-            if (lookup.hasOwnProperty(s)) return lookup[s];
+            if (ts.hasProperty(lookup, s)) return lookup[s];
             return lookup[s] = func(s);
         }) as Memoized<T>;
         run.reset = () => {
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 3ab9f02741cc1..7b8e091a96205 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -940,7 +940,7 @@ namespace ts.server {
                 // raw is now fixed and ready
                 this.safelist = raw.typesMap;
                 for (const key in raw.simpleMap) {
-                    if (raw.simpleMap.hasOwnProperty(key)) {
+                    if (hasProperty(raw.simpleMap, key)) {
                         this.legacySafelist.set(key, raw.simpleMap[key].toLowerCase());
                     }
                 }
diff --git a/src/server/session.ts b/src/server/session.ts
index 4bdadd04a15fa..f0d26443dd522 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -297,7 +297,7 @@ namespace ts.server {
     interface ProjectNavigateToItems {
         project: Project;
         navigateToItems: readonly NavigateToItem[];
-    };
+    }
 
     function createDocumentSpanSet(): Set<DocumentSpan> {
         return createSet(({textSpan}) => textSpan.start + 100003 * textSpan.length, documentSpansEqual);
diff --git a/src/services/completions.ts b/src/services/completions.ts
index eb2933f3682ae..afea634c32b2c 100644
--- a/src/services/completions.ts
+++ b/src/services/completions.ts
@@ -1107,7 +1107,7 @@ namespace ts.Completions {
 
         return { isSnippet, insertText, labelDetails };
 
-    };
+    }
 
     function createObjectLiteralMethod(
         symbol: Symbol,
@@ -4335,7 +4335,7 @@ namespace ts.Completions {
 
     function isArrowFunctionBody(node: Node) {
         return node.parent && isArrowFunction(node.parent) && node.parent.body === node;
-    };
+    }
 
     /** True if symbol is a type or a module containing at least one type. */
     function symbolCanBeReferencedAtTypeLocation(symbol: Symbol, checker: TypeChecker, seenModules = new Map<SymbolId, true>()): boolean {
diff --git a/src/services/formatting/rules.ts b/src/services/formatting/rules.ts
index 637201b0c2546..85e67eb8cbb59 100644
--- a/src/services/formatting/rules.ts
+++ b/src/services/formatting/rules.ts
@@ -411,23 +411,23 @@ namespace ts.formatting {
     }
 
     function isOptionEnabled(optionName: keyof FormatCodeSettings): (context: FormattingContext) => boolean {
-        return (context) => context.options && context.options.hasOwnProperty(optionName) && !!context.options[optionName];
+        return (context) => context.options && hasProperty(context.options, optionName) && !!context.options[optionName];
     }
 
     function isOptionDisabled(optionName: keyof FormatCodeSettings): (context: FormattingContext) => boolean {
-        return (context) => context.options && context.options.hasOwnProperty(optionName) && !context.options[optionName];
+        return (context) => context.options && hasProperty(context.options, optionName) && !context.options[optionName];
     }
 
     function isOptionDisabledOrUndefined(optionName: keyof FormatCodeSettings): (context: FormattingContext) => boolean {
-        return (context) => !context.options || !context.options.hasOwnProperty(optionName) || !context.options[optionName];
+        return (context) => !context.options || !hasProperty(context.options, optionName) || !context.options[optionName];
     }
 
     function isOptionDisabledOrUndefinedOrTokensOnSameLine(optionName: keyof FormatCodeSettings): (context: FormattingContext) => boolean {
-        return (context) => !context.options || !context.options.hasOwnProperty(optionName) || !context.options[optionName] || context.TokensAreOnSameLine();
+        return (context) => !context.options || !hasProperty(context.options, optionName) || !context.options[optionName] || context.TokensAreOnSameLine();
     }
 
     function isOptionEnabledOrUndefined(optionName: keyof FormatCodeSettings): (context: FormattingContext) => boolean {
-        return (context) => !context.options || !context.options.hasOwnProperty(optionName) || !!context.options[optionName];
+        return (context) => !context.options || !hasProperty(context.options, optionName) || !!context.options[optionName];
     }
 
     function isForContext(context: FormattingContext): boolean {
diff --git a/src/services/refactors/convertExport.ts b/src/services/refactors/convertExport.ts
index cb79dd2672fa4..ffde52b9571ab 100644
--- a/src/services/refactors/convertExport.ts
+++ b/src/services/refactors/convertExport.ts
@@ -54,7 +54,7 @@ namespace ts.refactor {
         readonly exportName: Identifier; // This is exportNode.name except for VariableStatement_s.
         readonly wasDefault: boolean;
         readonly exportingModuleSymbol: Symbol;
-    };
+    }
 
     function getInfo(context: RefactorContext, considerPartialSpans = true): ExportInfo | RefactorErrorInfo | undefined {
         const { file, program } = context;
diff --git a/src/services/refactors/convertToOptionalChainExpression.ts b/src/services/refactors/convertToOptionalChainExpression.ts
index ba40ec6a5e553..a8c13e42f94fc 100644
--- a/src/services/refactors/convertToOptionalChainExpression.ts
+++ b/src/services/refactors/convertToOptionalChainExpression.ts
@@ -51,7 +51,7 @@ namespace ts.refactor.convertToOptionalChainExpression {
         finalExpression: PropertyAccessExpression | ElementAccessExpression | CallExpression,
         occurrences: Occurrence[],
         expression: ValidExpression,
-    };
+    }
 
     type ValidExpressionOrStatement = ValidExpression | ValidStatement;
 
@@ -119,7 +119,7 @@ namespace ts.refactor.convertToOptionalChainExpression {
     function getBinaryInfo(expression: BinaryExpression): OptionalChainInfo | RefactorErrorInfo | undefined {
         if (expression.operatorToken.kind !== SyntaxKind.AmpersandAmpersandToken) {
             return { error: getLocaleSpecificMessage(Diagnostics.Can_only_convert_logical_AND_access_chains) };
-        };
+        }
         const finalExpression = getFinalExpressionInChain(expression.right);
 
         if (!finalExpression) return { error: getLocaleSpecificMessage(Diagnostics.Could_not_find_convertible_access_expression) };
diff --git a/src/services/refactors/helpers.ts b/src/services/refactors/helpers.ts
index e86229af915d1..25fcc1a3f5bc1 100644
--- a/src/services/refactors/helpers.ts
+++ b/src/services/refactors/helpers.ts
@@ -5,7 +5,7 @@ namespace ts.refactor {
      */
     export interface RefactorErrorInfo {
         error: string;
-    };
+    }
 
     /**
      * Checks if some refactor info has refactor error info.
diff --git a/src/services/refactors/moveToNewFile.ts b/src/services/refactors/moveToNewFile.ts
index 287178169e6c1..b01218a95ba5a 100644
--- a/src/services/refactors/moveToNewFile.ts
+++ b/src/services/refactors/moveToNewFile.ts
@@ -97,7 +97,7 @@ namespace ts.refactor {
         // Filters imports and prologue directives out of the range of statements to move.
         // Imports will be copied to the new file anyway, and may still be needed in the old file.
         // Prologue directives will be copied to the new file and should be left in the old file.
-        return !isPureImport(statement) && !isPrologueDirective(statement);;
+        return !isPureImport(statement) && !isPrologueDirective(statement);
     }
 
     function isPureImport(node: Node): boolean {
diff --git a/src/services/stringCompletions.ts b/src/services/stringCompletions.ts
index 922e50654bbe1..33b508017683a 100644
--- a/src/services/stringCompletions.ts
+++ b/src/services/stringCompletions.ts
@@ -935,7 +935,7 @@ namespace ts.Completions.StringCompletions {
                 const dependencies: object | undefined = (contents as any)[key];
                 if (!dependencies) continue;
                 for (const dep in dependencies) {
-                    if (dependencies.hasOwnProperty(dep) && !startsWith(dep, "@types/")) {
+                    if (hasProperty(dependencies, dep) && !startsWith(dep, "@types/")) {
                         result.push(dep);
                     }
                 }
diff --git a/src/testRunner/unittests/tsbuild/outputPaths.ts b/src/testRunner/unittests/tsbuild/outputPaths.ts
index 72374f846115f..3bcad56dd68ab 100644
--- a/src/testRunner/unittests/tsbuild/outputPaths.ts
+++ b/src/testRunner/unittests/tsbuild/outputPaths.ts
@@ -19,7 +19,7 @@ namespace ts {
 
             it("verify getOutputFileNames", () => {
                 const sys = new fakes.System(input.fs().makeReadonly(), { executingFilePath: "/lib/tsc" }) as TscCompileSystem;
-                ;
+
                 assert.deepEqual(
                     getOutputFileNames(
                         parseConfigFileWithSystem("/src/tsconfig.json", {}, /*extendedConfigCache*/ undefined, {}, sys, noop)!,
diff --git a/src/testRunner/unittests/tsserver/helpers.ts b/src/testRunner/unittests/tsserver/helpers.ts
index 8d7be8e8ae4ab..323e07a876d1a 100644
--- a/src/testRunner/unittests/tsserver/helpers.ts
+++ b/src/testRunner/unittests/tsserver/helpers.ts
@@ -836,7 +836,7 @@ namespace ts.projectSystem {
         checkAllErrors(request);
     }
 
-    interface SkipErrors { semantic?: true; suggestion?: true };
+    interface SkipErrors { semantic?: true; suggestion?: true }
     export interface CheckAllErrors extends VerifyGetErrRequestBase {
         files: readonly any[];
         skip?: readonly (SkipErrors | undefined)[];
diff --git a/src/testRunner/unittests/tsserver/projects.ts b/src/testRunner/unittests/tsserver/projects.ts
index 84d09a3dbda25..10cc61ff6cd03 100644
--- a/src/testRunner/unittests/tsserver/projects.ts
+++ b/src/testRunner/unittests/tsserver/projects.ts
@@ -567,7 +567,7 @@ namespace ts.projectSystem {
                 path: "/a/b/file1.js",
                 content: "var x = 10;",
                 fileName: "/a/b/file1.js",
-                scriptKind: "JS" as "JS"
+                scriptKind: "JS" as const
             };
 
             const host = createServerHost([]);