---
sidebar_position: 5
title: Exchange Operations
---

# Exchange Operations Guide

TronWeb provides built-in support for the Bancor-based decentralized exchange (DEX) protocol on TRON. This allows creating token trading pairs and executing trades on-chain.

:::note
TRON's built-in DEX uses the **Bancor algorithm** for automated price discovery based on token supply and balance ratios.
:::

## Creating an Exchange

### TRX-to-Token Exchange

Create a trading pair between TRX and a TRC-10 token:

```javascript
const tx = await tronWeb.transactionBuilder.createTRXExchange(
    'TokenName',   // TRC-10 token name
    1000000000,    // token amount to deposit
);
const signedTx = await tronWeb.trx.sign(tx);
const receipt = await tronWeb.trx.sendRawTransaction(signedTx);
```

### Token-to-Token Exchange

Create a trading pair between two TRC-10 tokens:

```javascript
const tx = await tronWeb.transactionBuilder.createTokenExchange(
    'TokenA',      // first token name
    1000000000,    // first token amount
    'TokenB',      // second token name
    2000000000,    // second token amount
);
const signedTx = await tronWeb.trx.sign(tx);
const receipt = await tronWeb.trx.sendRawTransaction(signedTx);
```

## Managing Exchange Liquidity

### Inject Tokens

Add liquidity to an existing exchange:

```javascript
const tx = await tronWeb.transactionBuilder.injectExchangeTokens(
    exchangeId,    // exchange ID
    'TokenName',   // token to inject
    1000000000,    // amount to inject
);
const signedTx = await tronWeb.trx.sign(tx);
const receipt = await tronWeb.trx.sendRawTransaction(signedTx);
```

### Withdraw Tokens

Remove liquidity from an exchange:

```javascript
const tx = await tronWeb.transactionBuilder.withdrawExchangeTokens(
    exchangeId,    // exchange ID
    'TokenName',   // token to withdraw
    500000000,     // amount to withdraw
);
const signedTx = await tronWeb.trx.sign(tx);
const receipt = await tronWeb.trx.sendRawTransaction(signedTx);
```

## Trading

Execute a trade on an exchange:

```javascript
const tx = await tronWeb.transactionBuilder.tradeExchangeTokens(
    exchangeId,    // exchange ID
    'TokenName',   // token to sell
    1000000000,    // amount to sell
    500000000,     // expected minimum amount to receive
);
const signedTx = await tronWeb.trx.sign(tx);
const receipt = await tronWeb.trx.sendRawTransaction(signedTx);
```

**Parameters:**

| Parameter | Type | Description |
|-----------|------|-------------|
| `exchangeID` | number | The exchange pair ID |
| `tokenName` | string | Token you are selling |
| `tokenAmountSold` | number | Amount of token to sell |
| `tokenAmountExpected` | number | Minimum amount expected to receive (slippage protection) |

:::tip
Set `tokenAmountExpected` to provide slippage protection. The trade will fail if the actual received amount is less than this value.
:::

## Querying Exchanges

```javascript
// List all exchanges
const exchanges = await tronWeb.trx.listExchanges();

// Get details of a specific exchange
const exchange = await tronWeb.trx.getExchangeByID(exchangeId);
console.log(exchange);
// {
//   exchange_id: 1,
//   creator_address: '...',
//   first_token_id: 'TokenA',
//   first_token_balance: 1000000000,
//   second_token_id: '_',  // '_' represents TRX
//   second_token_balance: 5000000000,
// }

// List exchanges created by a specific account
const myExchanges = await tronWeb.trx.listExchangesPaginated(limit, offset);
```

## Bancor Price Calculation

The Bancor algorithm ensures that:

```
first_token_balance × second_token_balance = constant
```

When you sell token A to buy token B:

```
Amount of B received = second_balance - (first_balance × second_balance) / (first_balance + amount_of_A_sold)
```

This means larger trades have higher price impact (slippage).

## Related API References

- [transactionBuilder.injectExchangeTokens](../API%20List/transactionBuilder/injectExchangeTokens.md)
- [transactionBuilder.withdrawExchangeTokens](../API%20List/transactionBuilder/withdrawExchangeTokens.md)
- [transactionBuilder.tradeExchangeTokens](../API%20List/transactionBuilder/tradeExchangeTokens.md)