JavaScript & Node.js Real-time WebSocket client library for Forex, Cryptocurrency, and Stock market data from FCS API.
This library uses WebSocket protocol to stream live market data. Works seamlessly in both Browser (JavaScript) and Node.js environments.
- Real-time WebSocket - Live price updates via WebSocket connection
- Multi-Market Support - Forex, Crypto, and Stock data in one library
- Universal - Works in Browser (Vanilla JS) and Node.js
- Auto-Reconnect - Handles WebSocket connection drops automatically
- Tab Visibility - Smart disconnect when browser tab is hidden (saves bandwidth)
- Heartbeat - Built-in WebSocket keep-alive mechanism
- Lightweight - No dependencies for browser usage
Use demo API key for testing: fcs_socket_demo
npm install fcsapi-websocketconst FCSClient = require('fcsapi-websocket');<script src="https://cdn.jsdelivr.net/gh/fcsapi/websocket-js/fcs-client-lib.js"></script><script src="fcs-client-lib.js"></script><!DOCTYPE html>
<html>
<head>
<title>FCS Real-time Data</title>
<script src="fcs-client-lib.js"></script>
</head>
<body>
<div id="price"></div>
<script>
const client = new FCSClient('YOUR_API_KEY');
client.onmessage = (data) => {
// Handle real-time price updates
if (data.type === 'price' && data.prices) {
const p = data.prices;
if (p.mode === 'candle' || p.mode === 'initial') {
document.getElementById('price').innerText =
`${data.symbol}: $${p.c} (O:${p.o} H:${p.h} L:${p.l})`;
}
}
};
client.connect().then(() => {
// Subscribe to Bitcoin on 1 Day timeframe
client.join('BINANCE:BTCUSDT', '1D');
});
</script>
</body>
</html>const FCSClient = require('fcsapi-websocket');
const client = new FCSClient('YOUR_API_KEY');
client.onmessage = (data) => {
// Handle price updates
if (data.type === 'price' && data.prices) {
const p = data.prices;
if (p.mode === 'candle') {
console.log(`${data.symbol}: Open=${p.o} High=${p.h} Low=${p.l} Close=${p.c} Vol=${p.v}`);
} else if (p.mode === 'askbid') {
console.log(`${data.symbol}: Ask=${p.a} Bid=${p.b} Close=${p.c}`);
}
}
};
client.connect().then(() => {
// Subscribe to Bitcoin
client.join('BINANCE:BTCUSDT', '1D');
// Subscribe to Forex
client.join('FX:EURUSD', '1D');
});const client = new FCSClient(apiKey, url);| Parameter | Type | Default | Description |
|---|---|---|---|
apiKey |
string | required | Your FCS API key |
url |
string | wss://ws-v4.fcsapi.com/ws |
WebSocket server URL (optional) |
Connects to the WebSocket server. Returns a Promise.
client.connect().then(() => {
console.log('Connected!');
}).catch(err => {
console.error('Connection failed:', err);
});Manually closes the connection.
client.disconnect();Subscribe to a symbol for real-time updates.
// Forex
client.join('FX:EURUSD', '1m');
// Crypto
client.join('BINANCE:BTCUSDT', '1m');
// Stock
client.join('NASDAQ:AAPL', '1m');Unsubscribe from a symbol.
client.leave('FX:EURUSD', '1m');Unsubscribe from all symbols.
client.removeAll();| Callback | Description |
|---|---|
onconnected |
Fired when connection is established |
onmessage |
Fired when data is received |
onclose |
Fired when connection is closed |
onerror |
Fired when an error occurs |
onreconnect |
Fired when reconnection is successful |
client.onconnected = () => console.log('Connected!');
client.onmessage = (data) => console.log('Data:', data);
client.onclose = (event) => console.log('Closed:', event.code);
client.onerror = (err) => console.error('Error:', err);
client.onreconnect = () => console.log('Reconnected!');| Property | Type | Default | Description |
|---|---|---|---|
reconnectDelay |
number | 3000 | Delay (ms) before reconnection attempt |
reconnectlimit |
number | 5 | Maximum reconnection attempts |
focusTimeout |
number | 3 | Minutes before disconnect when tab is hidden (0 = never) |
const client = new FCSClient('YOUR_API_KEY');
client.reconnectDelay = 5000; // 5 seconds
client.reconnectlimit = 10; // 10 attempts
client.focusTimeout = 5; // 5 minutesThe WebSocket sends different message types:
{
"type": "message",
"success": true,
"message": "Successfully joined room: BINANCE:BTCUSDT_1D_0s",
"room": "BINANCE:BTCUSDT_1D_0s",
"symbol": "BTCUSDT",
"timeframe": "1D",
"short": "joined_room"
}{
"type": "price",
"symbol": "BINANCE:BTCUSDT",
"timeframe": "1D",
"prices": {
"mode": "profile",
"profile": {
"current_session": "market",
"timezone": "Etc/UTC",
"pro_name": "BINANCE:BTCUSDT",
"update_mode": "streaming"
}
}
}{
"type": "price",
"symbol": "BINANCE:BTCUSDT",
"timeframe": "1D",
"prices": {
"mode": "initial",
"t": 1766361600, // Timestamp (Unix seconds)
"o": 88658.87, // Open price
"h": 90588.23, // High price
"l": 87900, // Low price
"c": 89962.61, // Close price
"v": 0.247 // Volume
}
}Primary update mode - contains all price data including OHLCV and Ask/Bid.
{
"type": "price",
"symbol": "BINANCE:BTCUSDT",
"timeframe": "1D",
"prices": {
"mode": "candle",
"t": 1766361600, // Timestamp
"o": 88658.87, // Open
"h": 90588.23, // High
"l": 87900, // Low
"c": 89962.61, // Close
"v": 8192.70, // Volume
"a": 89962.62, // Ask price
"b": 89962.61 // Bid price
}
}Sent when only Ask/Bid data changes. All values in this message are updated.
{
"type": "price",
"symbol": "BINANCE:BTCUSDT",
"timeframe": "1D",
"prices": {
"mode": "askbid",
"update": 1766411426, // Update timestamp
"c": 89962.61, // Close price
"a": 89962.62, // Ask price
"b": 89962.61, // Bid price
"t": 1766361600 // Candle timestamp
}
}client.onmessage = (data) => {
if (data.type === 'price' && data.prices) {
const p = data.prices;
const symbol = data.symbol;
switch (p.mode) {
case 'profile':
console.log(`${symbol} Profile loaded`);
break;
case 'initial':
case 'candle':
// Candle mode contains all data: OHLCV + Ask/Bid
console.log(`${symbol}: O=${p.o} H=${p.h} L=${p.l} C=${p.c} V=${p.v} Ask=${p.a} Bid=${p.b}`);
break;
case 'askbid':
console.log(`${symbol}: Ask=${p.a} Bid=${p.b}`);
break;
}
}
};Symbols must include an exchange prefix:
| Market | Format | Examples |
|---|---|---|
| Forex | FX:PAIR |
FX:EURUSD, FX:GBPUSD, FX:USDJPY |
| Crypto | EXCHANGE:PAIR |
BINANCE:BTCUSDT, BINANCE:ETHUSDT |
| Stock | EXCHANGE:SYMBOL |
NASDAQ:AAPL, NYSE:TSLA |
| Timeframe | Description |
|---|---|
1 |
1 minute |
5 |
5 minutes |
15 |
15 minutes |
30 |
30 minutes |
1H |
1 hour |
4H |
4 hours |
1D |
1 day |
1W |
1 week |
1M |
1 month |
Check the /examples folder for complete working demos:
- forex-example.html - Real-time Forex prices
- crypto-example.html - Real-time Cryptocurrency prices
- stock-example.html - Real-time Stock prices
The library automatically handles browser tab visibility to save bandwidth:
- When tab is hidden for more than 3 minutes (configurable), connection is closed
- When tab becomes visible again, connection is automatically restored
- All subscriptions are automatically rejoined after reconnection
Set focusTimeout = 0 to disable this feature:
client.focusTimeout = 0; // Never disconnect when tab hiddenclient.onerror = (err) => {
console.error('WebSocket error:', err);
};
client.onclose = (event) => {
if (event.code !== 1000) {
console.error('Unexpected close:', event.code, event.reason);
}
};- Visit FCS API
- Sign up for a free account
- Get your API key from the dashboard
For complete API documentation, visit:
- Email: support@fcsapi.com
- Website: fcsapi.com
MIT License - see LICENSE file for details.