> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pumpevm.fun/llms.txt
> Use this file to discover all available pages before exploring further.

# Integration guide

> Connect, subscribe, and trade on the CLOB from JavaScript or TypeScript.

## Install

```bash theme={null}
npm install ws @types/ws
```

## JavaScript: browser WebSocket

```javascript theme={null}
const ws = new WebSocket('wss://api.pumpevm.fun/ws/v1/prediction/orderbook');

// Subscribe to order book
ws.onopen = () => {
  ws.send(JSON.stringify({
    type: 'subscribe',
    channel: 'orderbook',
    marketId: '0x...',
    outcome: 'YES',
  }));
};

// Handle messages
ws.onmessage = (event) => {
  const data = JSON.parse(event.data);

  switch (data.type) {
    case 'orderbook':
      console.log('Order Book:', data.data);
      break;
    case 'trade':
      console.log('Trade Executed:', data.data);
      break;
    case 'position':
      console.log('Position Updated:', data.data);
      break;
  }
};

function placeLimitOrder(marketId, outcome, side, price, size) {
  ws.send(JSON.stringify({
    type: 'place_order',
    data: { marketId, outcome, side, orderType: 'limit', price, size },
  }));
}

function placeMarketOrder(marketId, outcome, side, size) {
  ws.send(JSON.stringify({
    type: 'place_order',
    data: { marketId, outcome, side, orderType: 'market', size },
  }));
}

function cancelOrder(orderId) {
  ws.send(JSON.stringify({
    type: 'cancel_order',
    data: { orderId },
  }));
}
```

## TypeScript: Node.js client

```typescript theme={null}
import WebSocket from 'ws';

const ws = new WebSocket('wss://api.pumpevm.fun/ws/v1/prediction/orderbook', {
  headers: {
    Authorization: 'Bearer YOUR_API_KEY',
  },
});

ws.on('open', () => {
  console.log('Connected to CLOB WebSocket');
});

ws.on('message', (data) => {
  const message = JSON.parse(data.toString());
  console.log('Received:', message);
});

function subscribeToMarket(marketId: string, outcome: string) {
  ws.send(JSON.stringify({
    type: 'subscribe',
    channel: 'orderbook',
    marketId,
    outcome,
  }));
}

function placeOrder(
  marketId: string,
  outcome: string,
  side: 'buy' | 'sell',
  orderType: 'limit' | 'market',
  price?: number,
  size?: number,
) {
  const payload: any = {
    type: 'place_order',
    data: { marketId, outcome, side, orderType },
  };

  if (orderType === 'limit') payload.data.price = price;
  if (size) payload.data.size = size;

  ws.send(JSON.stringify(payload));
}
```

## Best practices

* **Use limit orders** to protect against unfavorable price movements.
* **Monitor the order book** to understand liquidity before placing orders.
* **Respect rate limits** — see [Errors & rate limits](/developers/clob/errors).
* **Handle errors gracefully** with retry logic for transient failures.
* **Keep the WebSocket alive** with ping/pong and automatic reconnection.
* **Test on Sepolia first** before deploying to mainnet.