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useCallback,
useEffect,
useMemo,
useRef,
useSyncExternalStore,
} from "react";
import type {
AvailableMetric,
FormattedMemory,
LeakAnalysis,
MemoryCritical,
MemoryInfo,
MemorySnapshot,
MemoryWarning,
Severity,
SnapshotDiff,
SupportLevel,
Trend,
UseMemoryMonitorOptions,
UseMemoryMonitorReturn,
} from "./types";
import {
DEFAULT_OPTIONS,
DEFAULT_SEVERITY,
DEFAULT_TREND,
SSR_FORMATTED_MEMORY,
} from "./constants";
import {
createStore,
readMemoryFromAPI,
countDOMNodes,
estimateEventListeners,
type MemoryStore,
} from "./store";
import {
isServer,
detectSupport,
createUnsupportedInfo,
hasLegacyMemoryAPI,
} from "./utils/detection";
import {
createFormattedMemory,
calculateUsagePercentage,
} from "./utils/formatting";
import { CircularBuffer } from "./utils/circularBuffer";
import { analyzeLeakProbability, calculateTrend } from "./utils/leakDetection";
/**
* A React hook for monitoring browser memory usage in real-time.
* Detects memory leaks, provides threshold alerts, and supports snapshot comparison.
*
* Features:
* - Real-time memory tracking (JS Heap, DOM Nodes)
* - Memory leak detection with configurable sensitivity
* - Threshold-based warnings (warning/critical levels)
* - Memory snapshot comparison
* - SSR compatible
* - Graceful degradation for unsupported browsers
*
* @param options - Configuration options
* @returns Memory monitoring state and control functions
*
* @example
* ```tsx
* // Basic usage
* function MemoryDisplay() {
* const { heapUsed, formatted, isSupported } = useMemoryMonitor();
*
* if (!isSupported) {
* return <p>Memory monitoring not available</p>;
* }
*
* return <p>Memory: {formatted.heapUsed}</p>;
* }
* ```
*
* @example
* ```tsx
* // With leak detection
* const monitor = useMemoryMonitor({
* enableHistory: true,
* leakDetection: { enabled: true, sensitivity: 'medium' },
* onLeakDetected: (analysis) => {
* console.warn('Leak detected:', analysis);
* },
* });
* ```
*
* @example
* ```tsx
* // With threshold alerts
* const monitor = useMemoryMonitor({
* thresholds: { warning: 70, critical: 90 },
* onWarning: (data) => console.warn('Memory warning:', data),
* onCritical: (data) => console.error('Memory critical:', data),
* });
* ```
*/
export function useMemoryMonitor(
options: UseMemoryMonitorOptions = {}
): UseMemoryMonitorReturn {
// Merge options with defaults
const mergedOptions = useMemo(
() => ({
...DEFAULT_OPTIONS,
...options,
thresholds: {
...DEFAULT_OPTIONS.thresholds,
...options.thresholds,
},
leakDetection: {
...DEFAULT_OPTIONS.leakDetection,
...options.leakDetection,
},
}),
[options]
);
const {
interval,
autoStart,
enabled,
enableHistory,
historySize,
thresholds,
leakDetection,
devMode,
trackDOMNodes,
trackEventListeners,
logToConsole,
disableInProduction,
fallbackStrategy,
} = mergedOptions;
// Check if we should disable in production
// eslint-disable-next-line @typescript-eslint/no-explicit-any
const shouldDisable = disableInProduction && typeof (globalThis as any).process !== "undefined" && (globalThis as any).process?.env?.NODE_ENV === "production";
// Store refs for callbacks to avoid re-renders
const onUpdateRef = useRef(options.onUpdate);
const onWarningRef = useRef(options.onWarning);
const onCriticalRef = useRef(options.onCritical);
const onLeakDetectedRef = useRef(options.onLeakDetected);
const onUnsupportedRef = useRef(options.onUnsupported);
// Update refs when callbacks change
useEffect(() => {
onUpdateRef.current = options.onUpdate;
onWarningRef.current = options.onWarning;
onCriticalRef.current = options.onCritical;
onLeakDetectedRef.current = options.onLeakDetected;
onUnsupportedRef.current = options.onUnsupported;
}, [options.onUpdate, options.onWarning, options.onCritical, options.onLeakDetected, options.onUnsupported]);
// Detect browser support
const browserSupport = useMemo(() => detectSupport(), []);
// Create store instance (persists across renders)
const storeRef = useRef<MemoryStore | null>(null);
if (!storeRef.current) {
storeRef.current = createStore();
}
const store = storeRef.current;
// Subscribe to store using useSyncExternalStore
const storeState = useSyncExternalStore(
store.subscribe,
store.getSnapshot,
store.getServerSnapshot
);
// History buffer
const historyBufferRef = useRef<CircularBuffer<MemoryInfo> | null>(null);
if (enableHistory && !historyBufferRef.current) {
historyBufferRef.current = new CircularBuffer<MemoryInfo>(historySize);
}
// Track previous historySize for resize detection
const prevHistorySizeRef = useRef<number>(historySize);
// Resize history buffer when historySize changes
useEffect(() => {
Iif (enableHistory && historyBufferRef.current && historySize !== prevHistorySizeRef.current) {
historyBufferRef.current.resize(historySize);
prevHistorySizeRef.current = historySize;
}
}, [enableHistory, historySize]);
// Snapshot storage
const snapshotsRef = useRef<Map<string, MemorySnapshot>>(new Map());
// Interval ID ref
const intervalIdRef = useRef<ReturnType<typeof setInterval> | null>(null);
// Previous severity for callback deduplication
const prevSeverityRef = useRef<Severity>(DEFAULT_SEVERITY);
// Previous leak status for callback deduplication
const prevLeakDetectedRef = useRef<boolean>(false);
// Monitoring state ref
const isMonitoringRef = useRef<boolean>(false);
// Determine if monitoring is supported
const isSupported = useMemo(() => {
Iif (isServer()) return false;
Iif (shouldDisable) return false;
if (fallbackStrategy === "none") {
return hasLegacyMemoryAPI();
}
// With fallback strategies, we can always provide some monitoring
return true;
}, [shouldDisable, fallbackStrategy]);
// Determine support level
const supportLevel: SupportLevel = useMemo(() => {
Iif (!isSupported) return "none";
return browserSupport.level;
}, [isSupported, browserSupport.level]);
// Available metrics
const availableMetrics: AvailableMetric[] = useMemo(() => {
Iif (!isSupported) return [];
return browserSupport.availableMetrics;
}, [isSupported, browserSupport.availableMetrics]);
// Calculate derived values
const memory = storeState.memory;
const heapUsed = memory?.heapUsed ?? null;
const heapTotal = memory?.heapTotal ?? null;
const heapLimit = memory?.heapLimit ?? null;
const usagePercentage = calculateUsagePercentage(heapUsed, heapLimit);
const domNodes = storeState.domNodes;
const eventListeners = storeState.eventListeners;
// Calculate severity based on thresholds
const severity = useMemo((): Severity => {
if (usagePercentage === null) return DEFAULT_SEVERITY;
if (usagePercentage >= (thresholds.critical ?? 90)) {
return "critical";
}
if (usagePercentage >= (thresholds.warning ?? 70)) {
return "warning";
}
return "normal";
}, [usagePercentage, thresholds.critical, thresholds.warning]);
// Calculate history and trend
const history = useMemo(() => {
if (!enableHistory || !historyBufferRef.current) return [];
return historyBufferRef.current.toArray();
}, [enableHistory, storeState.lastUpdated]);
const trend: Trend = useMemo(() => {
if (!enableHistory || history.length < 3) return DEFAULT_TREND;
return calculateTrend(history);
}, [enableHistory, history]);
// Leak analysis
const leakAnalysis = useMemo((): LeakAnalysis | null => {
Eif (!leakDetection.enabled || !enableHistory) return null;
const windowSize = leakDetection.windowSize ?? 10;
const samples = historyBufferRef.current?.getRecent(windowSize) ?? [];
Iif (samples.length < 5) return null;
return analyzeLeakProbability(
samples,
leakDetection.sensitivity ?? "medium",
leakDetection.threshold
);
}, [
leakDetection.enabled,
leakDetection.sensitivity,
leakDetection.windowSize,
leakDetection.threshold,
enableHistory,
history,
]);
const isLeakDetected = leakAnalysis?.isLeaking ?? false;
const leakProbability = leakAnalysis?.probability ?? 0;
// Formatted values
const formatted: FormattedMemory = useMemo(() => {
Iif (!isSupported) return SSR_FORMATTED_MEMORY;
return createFormattedMemory(memory, domNodes, eventListeners);
}, [isSupported, memory, domNodes, eventListeners]);
// Poll function
const poll = useCallback(() => {
Iif (!isSupported || !enabled) return;
// Read memory
const newMemory = readMemoryFromAPI();
if (newMemory) {
store.updateMemory(newMemory);
// Add to history
if (enableHistory && historyBufferRef.current) {
historyBufferRef.current.push(newMemory);
}
// Call onUpdate callback
onUpdateRef.current?.(newMemory);
// Log to console in dev mode
Iif (logToConsole && devMode) {
console.log("[useMemoryMonitor]", {
heapUsed: newMemory.heapUsed,
heapTotal: newMemory.heapTotal,
heapLimit: newMemory.heapLimit,
});
}
}
// Track DOM nodes if enabled
if (trackDOMNodes) {
const nodeCount = countDOMNodes();
store.updateDOMNodes(nodeCount);
}
// Track event listeners if enabled
if (trackEventListeners) {
const listenerCount = estimateEventListeners();
store.updateEventListeners(listenerCount);
}
}, [
isSupported,
enabled,
store,
enableHistory,
trackDOMNodes,
trackEventListeners,
logToConsole,
devMode,
]);
// Start monitoring
const start = useCallback(() => {
Iif (!isSupported || !enabled || isMonitoringRef.current) return;
isMonitoringRef.current = true;
store.updateMonitoringStatus(true);
// Initial poll
poll();
// Set up interval
intervalIdRef.current = setInterval(poll, interval);
Iif (devMode && logToConsole) {
console.log("[useMemoryMonitor] Monitoring started");
}
}, [isSupported, enabled, store, poll, interval, devMode, logToConsole]);
// Stop monitoring
const stop = useCallback(() => {
if (!isMonitoringRef.current) return;
isMonitoringRef.current = false;
store.updateMonitoringStatus(false);
Eif (intervalIdRef.current) {
clearInterval(intervalIdRef.current);
intervalIdRef.current = null;
}
Iif (devMode && logToConsole) {
console.log("[useMemoryMonitor] Monitoring stopped");
}
}, [store, devMode, logToConsole]);
// Take snapshot
const takeSnapshot = useCallback(
(id: string): MemorySnapshot | null => {
if (!isSupported || !memory) return null;
const snapshot: MemorySnapshot = {
id,
memory: { ...memory },
domNodes: domNodes ?? undefined,
eventListeners: eventListeners ?? undefined,
timestamp: Date.now(),
};
snapshotsRef.current.set(id, snapshot);
return snapshot;
},
[isSupported, memory, domNodes, eventListeners]
);
// Compare snapshots
const compareSnapshots = useCallback(
(id1: string, id2: string): SnapshotDiff | null => {
const snapshot1 = snapshotsRef.current.get(id1);
const snapshot2 = snapshotsRef.current.get(id2);
if (!snapshot1 || !snapshot2) return null;
return {
heapDelta: snapshot2.memory.heapUsed - snapshot1.memory.heapUsed,
heapPercentChange:
snapshot1.memory.heapUsed > 0
? ((snapshot2.memory.heapUsed - snapshot1.memory.heapUsed) /
snapshot1.memory.heapUsed) *
100
: 0,
domNodesDelta:
snapshot1.domNodes != null && snapshot2.domNodes != null
? snapshot2.domNodes - snapshot1.domNodes
: undefined,
eventListenersDelta:
snapshot1.eventListeners != null && snapshot2.eventListeners != null
? snapshot2.eventListeners - snapshot1.eventListeners
: undefined,
timeDelta: snapshot2.timestamp - snapshot1.timestamp,
};
},
[]
);
// Clear history
const clearHistory = useCallback(() => {
Eif (historyBufferRef.current) {
historyBufferRef.current.clear();
}
}, []);
// Request GC (hint only, NOT guaranteed in standard browsers)
// JavaScript cannot force GC - this only works with --expose-gc flag
const requestGC = useCallback(() => {
Iif (isServer()) return;
// Only works with Chrome/Node.js launched with --expose-gc flag
// In standard browsers, gc() does not exist
// eslint-disable-next-line @typescript-eslint/no-explicit-any
Iif (typeof (globalThis as any).gc === "function") {
try {
// eslint-disable-next-line @typescript-eslint/no-explicit-any
(globalThis as any).gc();
if (devMode && logToConsole) {
console.log("[useMemoryMonitor] GC triggered via --expose-gc");
}
return;
} catch {
// gc() exists but failed
}
}
// Note: No reliable fallback exists for standard browsers.
// V8 engine controls GC timing based on its own heuristics.
Iif (devMode && logToConsole) {
console.warn(
"[useMemoryMonitor] GC not available. " +
"Use Chrome/Node.js with --expose-gc flag to enable manual GC."
);
}
}, [devMode, logToConsole]);
// Auto-start effect
useEffect(() => {
if (autoStart && isSupported && enabled && !shouldDisable) {
start();
}
return () => {
stop();
};
}, [autoStart, isSupported, enabled, shouldDisable, start, stop]);
// Visibility change effect (pause when tab is hidden)
useEffect(() => {
Iif (isServer()) return;
const handleVisibilityChange = () => {
if (document.hidden) {
stop();
} else if (autoStart && isSupported && enabled) {
start();
}
};
document.addEventListener("visibilitychange", handleVisibilityChange);
return () => {
document.removeEventListener("visibilitychange", handleVisibilityChange);
};
}, [autoStart, isSupported, enabled, start, stop]);
// Severity change callback effect
useEffect(() => {
if (severity === prevSeverityRef.current) return;
const prevSeverity = prevSeverityRef.current;
prevSeverityRef.current = severity;
Iif (!memory || !usagePercentage) return;
const callbackData = {
memory,
usagePercentage,
threshold: severity === "critical" ? (thresholds.critical ?? 90) : (thresholds.warning ?? 70),
timestamp: Date.now(),
};
// Only call callback when severity increases
if (severity === "warning" && prevSeverity === "normal") {
onWarningRef.current?.(callbackData as MemoryWarning);
E} else if (severity === "critical") {
onCriticalRef.current?.(callbackData as MemoryCritical);
}
}, [severity, memory, usagePercentage, thresholds.warning, thresholds.critical]);
// Leak detection callback effect
useEffect(() => {
Eif (!leakAnalysis) return;
if (isLeakDetected && !prevLeakDetectedRef.current) {
onLeakDetectedRef.current?.(leakAnalysis);
}
prevLeakDetectedRef.current = isLeakDetected;
}, [isLeakDetected, leakAnalysis]);
// Unsupported callback effect
useEffect(() => {
Iif (!isSupported && onUnsupportedRef.current) {
const unsupportedInfo = createUnsupportedInfo();
onUnsupportedRef.current(unsupportedInfo);
}
}, [isSupported]);
// SSR early return
Iif (isServer()) {
return {
memory: null,
heapUsed: null,
heapTotal: null,
heapLimit: null,
usagePercentage: null,
domNodes: null,
eventListeners: null,
isSupported: false,
isMonitoring: false,
isLeakDetected: false,
severity: DEFAULT_SEVERITY,
supportLevel: "none",
availableMetrics: [],
history: [],
trend: DEFAULT_TREND,
leakProbability: 0,
start: () => {},
stop: () => {},
takeSnapshot: () => null,
compareSnapshots: () => null,
clearHistory: () => {},
requestGC: () => {},
formatted: SSR_FORMATTED_MEMORY,
};
}
return {
// Current State
memory,
heapUsed,
heapTotal,
heapLimit,
usagePercentage,
// DOM Related
domNodes,
eventListeners,
// Status Flags
isSupported,
isMonitoring: storeState.isMonitoring,
isLeakDetected,
severity,
// Support Details
supportLevel,
availableMetrics,
// Analysis Data
history,
trend,
leakProbability,
// Actions
start,
stop,
takeSnapshot,
compareSnapshots,
clearHistory,
requestGC,
// Formatting
formatted,
};
}
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