refactor: convert all class components to function components (#431)

[nahrinoda]

Summary

Converts all 7 class components to function components with React hooks, consolidates all TypeScript type definitions into a single types.ts file, removes PropTypes in favor of TypeScript, and improves type safety — fully resolving #431.

Components converted

Component	Complexity	Key patterns used
ExpandIcon	Simple	React.memo, useCallback, JS default params
ColumnResizer	Complex	useRef for drag state, ref-based prop access for DOM listeners to avoid stale closures, useEffect cleanup
TableRow	Complex	useState, useRef, useMemo, split componentDidUpdate into multiple useEffect hooks for re-measurement cycle
TableHeader	Medium	forwardRef + useImperativeHandle (scrollTo, forceUpdate), useReducer for force-update trick
GridTable	Medium	forwardRef + useImperativeHandle (7 imperative methods), useMemo with memoize-one
Column	Trivial	Function returning null with static property assignments
BaseTable	Complex	useState (5 state vars), 17+ useRef instances, useMemo for memoized helpers, throttle/debounce with stable identity via useMemo, forwardRef + useImperativeHandle (14 public API methods), useEffect for lifecycle

Migration patterns

• React.PureComponent -> React.memo wrapper
• static defaultProps -> JS default parameters in destructuring
• Constructor .bind(this) -> useCallback hooks
• Instance variables -> useRef
• this.state / setState -> useState
• componentDidMount / componentDidUpdate -> useEffect
• componentWillUnmount -> useEffect cleanup return
• forceUpdate() -> useReducer counter trick
• Imperative class methods -> forwardRef + useImperativeHandle
• memoize-one calls -> useMemo(() => memoize(...), [])
• Throttled/debounced handlers -> useMemo with stable identity + useRef for latest props

Type consolidation

Moved all 14 component prop interfaces and handle types from individual component files into the central src/types.ts, joining the 15 types already there. All types are re-exported from index.ts for consumer access.

Types moved	Source file
AutoResizerProps	AutoResizer.tsx
BaseTableProps, BaseTableHandle	BaseTable.tsx
ColumnResizerProps	ColumnResizer.tsx
ExpandIconProps	ExpandIcon.tsx
GridTableProps, GridTableHandle	GridTable.tsx
SortIndicatorProps	SortIndicator.tsx
TableCellProps	TableCell.tsx
TableHeaderProps, TableHeaderHandle	TableHeader.tsx
TableHeaderCellProps	TableHeaderCell.tsx
TableHeaderRowProps	TableHeaderRow.tsx
TableRowProps	TableRow.tsx

Best practices applied

PropTypes removal — Removed PropTypes from all 12 component files (~520 lines deleted). TypeScript interfaces in types.ts fully supersede runtime prop validation. The ESLint react/prop-types rule is now disabled. PropTypes are removed from the React 19 package entirely.

Type safety improvements — Replaced loose [key: string]: any index signatures with React.HTMLAttributes<HTMLDivElement> in ColumnResizerProps, ExpandIconProps, and SortIndicatorProps. Remaining index signatures are documented with comments explaining they exist for legitimate pass-through patterns (e.g., GridTable forwarding props to react-window Grid, or row/header components spreading props to configurable tag elements).

Future migration paths

forwardRef deprecation (React 19) — forwardRef is deprecated in React 19; ref becomes a regular prop. Components using forwardRef (BaseTable, GridTable, TableHeader) can be simplified when upgrading. No action needed now.

React Compiler readiness — The React Compiler (v1.0, Oct 2025) auto-memoizes components, eliminating the need for React.memo, useCallback, and useMemo. The current code is compatible — these wrappers can be safely removed when adopting the compiler.

What is NOT changed

• No behavioral changes — the public API and rendering output are identical
• All import type usage is correct throughout (verified via audit)

Test plan

• All 22 existing snapshot tests pass unchanged
• ESLint passes with zero errors
• TypeScript build (tsc --emitDeclarationOnly) passes with zero errors
• Full build (Babel CJS/ESM + TypeScript declarations + Sass) completes successfully
• Manual verification of demo site examples (expand/collapse, column resize, sorting, frozen columns, dynamic row height, scrolling)

Screen.Recording.2026-06-19.at.4.39.19.PM.mov

Resolves #431