Why Cursor Generates Invalid JavaScript

1---
2description: Enforce JavaScript strict mode compliance
3globs: "*.js,*.jsx,*.mjs"
4alwaysApply: true
5---
6
7# Strict Mode Compliance
8- NEVER use undeclared variables (always use const, let, or var)
9- NEVER use the 'with' statement
10- NEVER use duplicate parameter names in functions
11- NEVER use octal numeric literals (0644) — use 0o644 instead
12- NEVER assign to read-only properties or undeletable properties
13- NEVER use 'arguments.callee' or 'arguments.caller'
14- NEVER use eval() to create variables in surrounding scope
15- ALWAYS declare variables before use
16- ALWAYS use 'use strict' at the top of .js files (or use ES modules)
17
18## TypeScript files are strict by default if tsconfig has strict: true

1// eslint.config.js
2import js from '@eslint/js';
3
4export default [
5  js.configs.recommended,
6  {
7    rules: {
8      'strict': ['error', 'safe'],
9      'no-undef': 'error',
10      'no-var': 'error',
11      'no-with': 'error',
12      'no-octal': 'error',
13      'no-eval': 'error',
14      'no-caller': 'error',
15      'no-implicit-globals': 'error',
16      'no-shadow-restricted-names': 'error',
17    },
18  },
19];

1Fix all strict mode violations in this code:
2- Add const/let declarations for any undeclared variables
3- Replace 'with' statements with explicit property access
4- Replace octal literals (0644) with ES6 octal syntax (0o644)
5- Remove duplicate function parameter names
6- Replace arguments.callee with named function references
7- Ensure 'use strict' is present at file top if not using ES modules

1{
2  "compilerOptions": {
3    "strict": true,
4    "noImplicitAny": true,
5    "strictNullChecks": true,
6    "strictFunctionTypes": true,
7    "strictBindCallApply": true,
8    "noImplicitThis": true,
9    "alwaysStrict": true,
10    "noUnusedLocals": true,
11    "noUnusedParameters": true,
12    "noImplicitReturns": true,
13    "noFallthroughCasesInSwitch": true
14  }
15}

1@strict-mode.mdc @codebase
2
3Search the codebase for JavaScript strict mode violations:
41. Variables used without declaration
52. 'with' statement usage
63. Duplicate function parameter names
74. Octal numeric literals without 0o prefix
85. eval() calls that create variables
96. arguments.callee or arguments.caller usage
107. Files missing 'use strict' that are not ES modules
11
12For each violation, show the file, line, and the fix.