javascript-coding-standards

Install eslint and prettier as dev dependencies, then extend airbnb-base and prettier in your .eslintrc.json. The provided configuration enables ES2022, ES modules, and rules like prefer-const, no-var, and arrow-body-style.

Use jest.mock() to stub module dependencies, then structure tests with describe/test blocks and the Arrange-Act-Assert pattern. The standards include examples with mockResolvedValue, rejects.toThrow for async errors, and test.each for parameterized cases.

The Jest configuration enforces 80% coverage for branches, functions, lines, and statements globally. Coverage is collected from src/**/*.js while excluding test files and index files.

Yes, it covers functional components with useState, useEffect, useCallback, and useMemo, plus custom hooks with cleanup functions to prevent state updates on unmounted components. Data fetching patterns include loading and error states.

Never hardcode secrets in source code. Load them with dotenv from environment variables and validate that all required variables exist at startup, throwing an error if any are missing.

var has function-scoped hoisting that causes subtle bugs, while == performs type coercion leading to unexpected comparisons. The standards enforce const/let and strict equality (===) through ESLint rules no-var and eqeqeq-style checks.