Listen to Trades

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Listen to Trades
In this guide, we will write a simple script using the Lyra.js package to listen to incoming trades and report on the position's profit and loss.
1. Setup Lyra.js
​Lyra.js is a JavaScript SDK for Optimistic Ethereum and the Lyra Protocol. It wraps around ethers and works in the web browser and Node.js.
To get started, clone the Lyra.js starter project:
git clone https://github.com/lyra-finance/lyra-js-starter.git
cd lyra-js-starter
Next, run yarn install to install node modules, including lyrafinance/lyra-js:
yarn install
2. Listen to trades
To listen to trades across all markets, simply initialize an onTrade listener which passes TradeEvent entities to a handler function. To get the position from a trade event, simply fetch its position edge. From a position,y ou can calculate its realized and unrealized profit and loss.
import Lyra from '@lyrafinance/lyra-js'
​
const lyra = new Lyra()
​
lyra.onTrade(async tradeEvent => {
​
    // Fetch position for trade
    const position = await tradeEvent.position()
    
    // Calculate realized and unrealized P&L
    const realizedPnl = position.realizedPnl()
    const unrealizedPnl = position.unrealizedPnl()
})
With this template, you can implement a variety of functionality:
Social trade feeds, such as a Discord or Twitter bot
Arbitrage bots which execute trades based on price updates.
Liquidation alerts for partially collateralized positions (combined with chainlink oracle price updates)
Execute a Trade (off chain)
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Last modified 1mo ago
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Outline
1. Setup Lyra.js
2. Listen to trades