SaltyCrane Cheat Sheets — Notes on JavaScript and web development

Flow Type Cheat Sheet

Flow is a static type checker for JavaScript. This is a list of Flow types generated from the source code in https://github.com/facebook/flow/tree/v0.111.3/ The script to generate this list is on github. Fixes welcome. See also my TypeScript cheat sheet, TypeScript React cheat sheet, and Docker cheat sheet.

There are separate sections for "private" or "magic" types with a $ in the name. See the note here and comment here. Update: Some these types are now documented here.
Links in bold point to the Flow documentation. Other links point to the Flow source code.

Flow version: v0.111.3 v0.110.1 v0.109.0 v0.108.0 v0.107.0 v0.106.3 v0.105.2 v0.104.0 v0.103.0 v0.102.0 v0.101.1 v0.100.0 v0.99.1 v0.98.1 v0.97.0 v0.96.1 v0.95.2 v0.94.0 v0.93.0 v0.92.1 v0.91.0 v0.90.0 v0.89.0 v0.88.0 v0.87.0 v0.86.0 v0.85.0 v0.84.0 v0.83.0 v0.82.0 v0.81.0 v0.80.0 v0.79.1 v0.78.0 v0.77.0 v0.76.0 v0.75.0 v0.74.0 v0.73.0 v0.72.0 v0.71.0 v0.70.0 v0.69.0 v0.68.0 v0.67.0 v0.66.0 v0.65.0 v0.64.0 v0.63.1 v0.62.0 v0.61.0 v0.60.1 v0.59.0 v0.58.0 v0.57.3 v0.56.0 v0.55.0 v0.54.0 v0.53.1 v0.52.0 v0.51.1 v0.50.0 v0.49.1 v0.48.0 v0.47.0 v0.46.0 v0.45.0

Contents

Built-in types
Core
React
React DOM
Document Object Model (DOM)
Browser Object Model (BOM)
CSS Object Model (CSSOM)
indexedDB
Node.js
Service Workers
Streams
International
WebAssembly

Core

Array<T> (class)
ArrayBuffer (class)
AsyncIterable<+T> (type)
AsyncIterator<+T> (type)
Boolean (class)
CallSite (class)
console (var)
DataView (class)
Date (class)
Error (class)
EvalError (class)
exports (var)
Float32Array (class)
Float64Array (class)
Function (class)
global (var)
Infinity (var)
Int16Array (class)

Int32Array (class)
Int8Array (class)
IntervalID (opaque type)
Iterable<+T> (type)
Iterator<+T> (type)
IteratorResult<+Yield,+Return> (type)
JSON (class)
Map<K, V> (class)
Math (var)
module (var)
NaN (var)
Number (class)
Object (class)
Promise<+R> (class)
PropertyDescriptor<T> (type)
PropertyDescriptorMap (type)
Proxy<T> (class)
RangeError (class)

ReferenceError (class)
Reflect (var)
RegExp (class)
require (var)
Set<T> (class)
String (class)
Symbol (class)
SyntaxError (class)
TimeoutID (opaque type)
TypeError (class)
Uint16Array (class)
Uint32Array (class)
Uint8Array (class)
Uint8ClampedArray (class)
undefined (var)
URIError (class)

Core "private" types

$ArrayBufferView (type)
$ArrayLike<T> (type)
$Flow$ModuleRef<T> (opaque type)
$NotNullOrVoid (type)
$ReadOnlyArray<+T> (class)
$ReadOnlyMap<K, +V> (class)
$ReadOnlySet<T> (class)
$ReadOnlyWeakMap<K: {...} | $ReadOnlyArray<mixed>, +V> (class)
$ReadOnlyWeakSet<T: {...} | $ReadOnlyArray<any>> (class)
$SymboIsConcatSpreadable mixins Symbol (class)

$SymbolHasInstance mixins Symbol (class)
$SymbolIterator mixins Symbol (class)
$SymbolMatch mixins Symbol (class)
$SymbolMatchAll mixins Symbol (class)
$SymbolReplace mixins Symbol (class)
$SymbolSearch mixins Symbol (class)
$SymbolSpecies mixins Symbol (class)
$SymbolSplit mixins Symbol (class)
$SymbolToPrimitive mixins Symbol (class)
$SymbolToStringTag mixins Symbol (class)

$SymbolUnscopables mixins Symbol (class)
$TypedArray (class)
Proxy$revocable<T> (type)
Proxy$traps<T> (type)
RegExp$flags (type)
RegExp$matchResult (type)
WeakMap<K: {...} | $ReadOnlyArray<mixed>, V> (class)
WeakSet<T: {...} | $ReadOnlyArray<any>> (class)

React

LegacyReactComponent<Props, State> (class)
react (module)
- Children (var)
- ChildrenArray<T> (type)
- cloneElement (var)
- Component (var)
- ComponentType<Props> (type)
- ConcurrentMode (var)
- Config<Props, DefaultProps> (type)
- Context<T> (type)
- createClass (var)
- createElement (var)
- Dispatch<A> = (A) (type)

DOM (var)
Element<typeof Component> (type)
ElementConfig<C> (type)
ElementProps<typeof Component> (type)
ElementRef<typeof Component> (type)
ElementType (type)
Fragment (var)
Interaction (type)
Key (type)
MaybeCleanUpFn (type)
MixedElement (type)
Node (type)
Portal (type)

Profiler (var)
ProfilerOnRenderFnType (type)
PropTypes (var)
PureComponent (var)
Ref<typeof Component> (type)
StatelessFunctionalComponent<Props> (type)
StrictMode (var)
Suspense (var)
version (var)

React "private" types

React$AbstractComponentStatics (type)
React$Component<Props, State = void> (class)
React$ComponentType<-Config> (type)
React$Context<T> (type)
React$Element<+ElementType: React$ElementType> (type)
React$ElementType (type)
React$Key (type)

React$PropTypes$oneOfType (type)
React$PropTypes$shape (type)
React$PureComponent<Props, State = void> (class)
React$Ref<ElementType: React$ElementType> (type)
React$StatelessFunctionalComponent<Props> (type)

React DOM

react-dom (module)
- version (var)
react-dom/server (module)
- version (var)
react-dom/test-utils (module)
- Simulate (var)
SyntheticAnimationEvent< +T: EventTarget = EventTarget,> (class)

React DOM "private" types

$JSXIntrinsics (type)

ReactDOM$HTMLElementJSXIntrinsic (type)

ReactDOM$SVGElementJSXIntrinsic (type)

Document Object Model (DOM)

Document Object Model (DOM) "private" types

ClipboardEvent$Init (type)
CustomEvent$Init (type)

Event$Init (type)
MouseEvent$MouseEventInit (type)

PointerEvent$PointerEventInit (type)
TransitionEvent$Init (type)

Browser Object Model (BOM)

MediaDeviceInfo (class)
MediaDevices (class)
MediaElementAudioSourceNode (class)
MediaQueryList (class)
MediaQueryListEvent (class)
MediaQueryListListener (type)
MediaStream (class)
MediaStreamAudioDestinationNode (class)
MediaStreamAudioSourceNode (class)
MediaStreamConstraints (type)
MediaStreamTrack (class)
MediaStreamTrackAudioSourceNode (class)
MediaStreamTrackEvent (class)
MediaTrackCapabilities (type)
MediaTrackSettings (type)
MediaTrackSupportedConstraints (type)
MessageChannel (class)
MessagePort (class)
MIDIAccess (class)
MIDIConnectionEvent (class)
MIDIInput (class)
MIDIInputMap (class)
MIDIMessageEvent (class)
MIDIOptions (type)
MIDIOutput (class)
MIDIOutputMap (class)
MidiPermissionDescriptor (type)
MIDIPort (class)
MIDIPortConnectionState (type)
MIDIPortDeviceState (type)
MIDIPortType (type)
MimeType (class)
MimeTypeArray (class)
ModeType (type)
MutationObserver (class)
MutationObserverInit (type)
MutationObserverInitRequired (type)
MutationRecord (class)
navigator (var)
Navigator mixins NavigatorID, NavigatorLanguage, NavigatorOnLine, NavigatorContentUtils, NavigatorCookies, NavigatorPlugins, NavigatorConcurrentHardware (class)
NavigatorConcurrentHardware (class)
NavigatorContentUtils (class)
NavigatorCookies (class)
NavigatorID (class)
NavigatorLanguage (class)
NavigatorOnLine (class)
NavigatorPlugins (class)
NodeFilter (var)
OfflineAudioCompletionEvent (class)
OfflineAudioContext (class)
OscillatorNode (class)
PannerNode (class)
Performance (class)
performance (var)
PerformanceEntry (class)
PerformanceEntryFilterOptions (type)
PerformanceEntryList (type)
PerformanceNavigation (class)
PerformanceNavigationTiming (class)
PerformanceObserver (class)
PerformanceObserverEntryList (interface)
PerformanceObserverInit (type)
PerformanceResourceTiming (class)
PerformanceTiming (class)

Browser Object Model (BOM) "private" types

TextDecoder$availableEncodings (type)
TextEncoder$availableEncodings (type)

CSS Object Model (CSSOM)

CSS Object Model (CSSOM) "private" types

AnimationPlaybackEvent$Init (type)

indexedDB

IDBCursor (interface)
IDBCursorWithValue (interface)
IDBDatabase (interface)
IDBDirection (type)

IDBEnvironment (interface)
IDBFactory (interface)
IDBIndex (interface)
IDBKeyRange (interface)

IDBObjectStore (interface)
IDBOpenDBRequest (interface)
IDBRequest (interface)
IDBTransaction (interface)

Node.js

__dirname (var)
__filename (var)
assert (module)
- AssertionError (class)
buffer (module)
- Buffer (var)
- INSPECT_MAX_BYTES (var)
- kMaxLength (var)
Buffer (class)
child_process (module)
- ChildProcess (var)
cluster (module)
- Cluster (class)
crypto (module)
- DEFAULT_ENCODING (var)
- Sign (class)
- Verify (class)
dgram (module)
dns (module)
- ADDRCONFIG (var)
- ADDRGETNETWORKPARAMS (var)
- BADFAMILY (var)
- BADFLAGS (var)
- BADHINTS (var)
- BADNAME (var)
- BADQUERY (var)
- BADRESP (var)
- BADSTR (var)
- CANCELLED (var)
- CONNREFUSED (var)
- DESTRUCTION (var)
- EOF (var)
- FILE (var)
- FORMER (var)
- LOADIPHLPAPI (var)
- LookupOptions (type)
- NODATA (var)
- NOMEM (var)
- NONAME (var)
- NOTFOUND (var)
- NOTIMP (var)
- NOTINITIALIZED (var)
- REFUSED (var)
- SERVFAIL (var)
- TIMEOUT (var)
- V4MAPPED (var)
domain (module)
duplexStreamOptions (type)
events (module)
- EventEmitter (class)
fs (module)
- BufferEncoding (type)
- constants (var)
- EncodingFlag (type)
- EncodingOptions (type)
- F_OK (var)
- FileHandle (class)
- FSPromise (class)
- FSPromisePath (type)
- FSWatcher (class)
- promises (var)
- R_OK (var)
- ReadStream (class)
- Stats (class)
- W_OK (var)
- WriteOptions (type)
- WriteStream (class)
- X_OK (var)
HeapSpaceStatistics (type)
HeapStatistics (type)
http (module)
- Agent (class)

ClientRequest (class)
globalAgent (var)
IncomingMessage (class)
METHODS (var)
Server (class)
ServerResponse (class)
STATUS_CODES (var)

https (module)
- Agent (class)
- ClientRequest (class)
- globalAgent (var)
- IncomingMessage (class)
- Server (class)
- ServerResponse (class)
net (module)
- connectionListener (type)
- connectListener (type)
- Server (class)
- Socket (class)
os (module)
- EOL (var)
path (module)
- delimiter (var)
- posix (var)
- sep (var)
- win32 (var)
process (var)
Process (class)
punycode (module)
- ucs2 (var)
- version (var)
querystring (module)
readableStreamOptions (type)
readline (module)
- Interface (var)
repl (module)
- Recoverable (class)
- REPL_MODE_MAGIC (var)
- REPL_MODE_SLOPPY (var)
- REPL_MODE_STRICT (var)
- REPLServer (class)
requestOptions (type)
stream (module)
- Duplex (var)
- PassThrough (var)
- Readable (var)
- Stream (var)
- Transform (var)
- Writable (var)
string_decoder (module)
- StringDecoder (var)
tls (module)
- CLIENT_RENEG_LIMIT (var)
- CLIENT_RENEG_WINDOW (var)
- DEFAULT_CIPHERS (var)
- DEFAULT_ECDH_CURVE (var)
- SecureContext (var)
- Server (var)
- SLAB_BUFFER_SIZE (var)
- TLSSocket (var)
transformStreamOptions (type)
tty (module)
- ReadStream (var)
- WriteStream (var)
url (module)
- URL (class)
- URLSearchParams (class)
util (module)
- TextDecoder (class)
- TextEncoder (class)
v8 (module)
vm (module)

Script (var)

writableStreamOptions (type)
zlib (module)
- codes (var)
- constants (var)
- deflate (var)
- Deflate (class)
- deflateRaw (var)
- DeflateRaw (class)
- deflateRawSync (var)
- deflateSync (var)
- gunzip (var)
- Gunzip (class)
- gunzipSync (var)
- gzip (var)
- Gzip (class)
- gzipSync (var)
- inflate (var)
- Inflate (class)
- inflateRaw (var)
- InflateRaw (class)
- inflateRawSync (var)
- inflateSync (var)
- unzip (var)
- Unzip (class)
- unzipSync (var)
- Z_ASCII (var)
- Z_BEST_COMPRESSION (var)
- Z_BEST_SPEED (var)
- Z_BINARY (var)
- Z_BLOCK (var)
- Z_BUF_ERROR (var)
- Z_DATA_ERROR (var)
- Z_DEFAULT_CHUNK (var)
- Z_DEFAULT_COMPRESSION (var)
- Z_DEFAULT_LEVEL (var)
- Z_DEFAULT_MEMLEVEL (var)
- Z_DEFAULT_STRATEGY (var)
- Z_DEFAULT_WINDOWBITS (var)
- Z_DEFLATED (var)
- Z_ERRNO (var)
- Z_FILTERED (var)
- Z_FINISH (var)
- Z_FIXED (var)
- Z_FULL_FLUSH (var)
- Z_HUFFMAN_ONLY (var)
- Z_MAX_CHUNK (var)
- Z_MAX_LEVEL (var)
- Z_MAX_MEMLEVEL (var)
- Z_MAX_WINDOWBITS (var)
- Z_MEM_ERROR (var)
- Z_MIN_CHUNK (var)
- Z_MIN_LEVEL (var)
- Z_MIN_MEMLEVEL (var)
- Z_MIN_WINDOWBITS (var)
- Z_NEED_DICT (var)
- Z_NO_COMPRESSION (var)
- Z_NO_FLUSH (var)
- Z_NULL (var)
- Z_OK (var)
- Z_PARTIAL_FLUSH (var)
- Z_RLE (var)
- Z_STREAM_END (var)
- Z_STREAM_ERROR (var)
- Z_SYNC_FLUSH (var)
- Z_TEXT (var)
- Z_TREES (var)
- Z_UNKNOWN (var)
- Z_VERSION_ERROR (var)
- Zlib (class)

Node.js "private" types

$SymbolReplModeMagic mixins Symbol (class)
$SymbolReplModeSloppy mixins Symbol (class)
$SymbolReplModeStrict mixins Symbol (class)
buffer$Encoding (type)
buffer$NonBufferEncoding (type)
buffer$ToJSONRet (type)
child_process$ChildProcess (class)
child_process$Error (class)
child_process$execCallback (type)
child_process$execFileCallback (type)
child_process$execFileOpts (type)
child_process$execFileSyncOpts (type)
child_process$execOpts (type)
child_process$execSyncOpts (type)
child_process$forkOpts (type)
child_process$Handle (type)
child_process$spawnOpts (type)
child_process$spawnRet (type)
child_process$spawnSyncOpts (type)
child_process$spawnSyncRet (type)
cluster$setupMasterOpts (type)
cluster$Worker (class)
crypto$Cipher (class)
crypto$createCredentialsDetails (type)
crypto$Credentials (type)
crypto$Decipher (class)
crypto$DiffieHellman (type)
crypto$ECDH (class)
crypto$ECDH$Encoding (type)

crypto$ECDH$Format (type)
crypto$Hash (class)
crypto$Hmac (class)
crypto$key (type)
crypto$Sign (class)
crypto$Sign$private_key (type)
crypto$Verify (class)
dgram$Socket (class)
dgram$Socket$rinfo (type)
domain$Domain (class)
events$EventEmitter (class)
http$Agent<+SocketT = net$Socket> (class)
http$agentOptions (type)
http$ClientRequest<+SocketT = net$Socket> (class)
http$IncomingMessage<SocketT = net$Socket> (class)
http$requestOptions (type)
http$Server (class)
http$ServerResponse (class)
https$requestOptions (type)
https$Server (class)
net$connectOptions (type)
net$Server (class)
net$Socket (class)
net$Socket$address (type)
os$CPU (type)
os$NetIFAddr (type)
os$UserInfo$buffer (type)
os$UserInfo$string (type)
process$CPUUsage (type)

Service Workers

Cache (class)
CacheQueryOptions (type)
caches (var)
CacheStorage (class)
Client (class)
ClientQueryOptions (type)
Clients (class)
clients (var)
ClientType (type)
ExtendableEvent (class)
ExtendableMessageEvent (class)
FetchEvent (class)
ForeignFetchOptions (type)

Streams

UnderlyingSink (interface)
UnderlyingSource (interface)
WritableStream (class)
WritableStreamController (interface)
WritableStreamWriter (interface)

International

FormatToPartsType (type)

Intl (var)

International "private" types

WebAssembly

TableDescriptor (type)
WebAssembly (var)

WebAssembly "private" types

WebAssembly$Table (class)