> For the complete documentation index, see [llms.txt](https://v1-docs.mint.club/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://v1-docs.mint.club/developers/mint.club-javascript-sdk/contract-interaction-react.js/buy-and-sell.md).

# Buy & Sell

## Constants

Following are the constant values used in examples below:

```javascript
export const BIG_TEN = new BigNumber(10);
export const DEFAULT_TOKEN_DECIMAL = 18;
```

## Buy

Buy contract call is as follows:

```javascript
mintClubBondContract.buy(
    tokenAddress,
    amount,
    minReward,
    beneficiary,
);
```

In order to calculate the minReward, we utilize the `getMintReward` function from `mintClubBondContract`.

```javascript
const contract = getMintClubBondContract();
const result = await contract.getMintReward(
  tokenAddress,
  truncateDecimals(new BigNumber(mintAmount).times(BIG_TEN.pow(DEFAULT_TOKEN_DECIMAL)).toString(), 0),
); // here mintAmount is amount of mint user is willing to spend

const outBN = new BigNumber(result[0].toString());
const minReward = truncateDecimals(
  outBN
    .times((100 - 2 /* slippage percentage */) / 100)
    .toFixed(0, 1)
    .toString(10),
  0,
);
```

`truncateDecimals` is a number helper function:

```javascript
export function truncateDecimals(num, digits = 18) {
  const str = num?.toString();

  if (str?.includes('.')) {
    const numbers = str.split('.');
    const decimals = numbers[1];
    if (digits === 0) {
      return numbers[0];
    } else if (decimals.length > digits) {
      return `${numbers[0]}.${numbers[1].toString().substring(0, digits)}`;
    }

    return num;
  }

  return num;
}
```

With the calculated values, we can now call the contract:

```javascript
import { AddressZero } from '@ethersproject/constants'; // use null address if there is no referrer wallet address
const tx = await mintClubBondContract.buy(tokenAddress, buyAmount, minReward, referrerWalletAddress);
```

## Sell

Sell contract call is as follows:

```javascript
mintClubBondContract.sell(
    tokenAddress,
    amount,
    minRefund, 
    beneficiary,
);
```

In order to calculate the minRefund, we utilize the `getBurnRefund` function from `mintClubBondContract`.

```javascript
const contract = getMintClubBondContract();
const result = await contract.getBurnRefund(
  tokenAddress,
  new BigNumber(amount).times(BIG_TEN.pow(DEFAULT_TOKEN_DECIMAL)).toString(),
); // here amount is amount of token user is willing to sell

const outBN = new BigNumber(result[0].toString());
const minRefund = outBN
                .times((100 - 2 /* slippage percentage */) / 100)
                .toFixed(0, 1)
                .toString(10);
```

With the calculated `minRefund` value, we can now call the sell function on `mintClubBondContract`.

```javascript
import { AddressZero } from '@ethersproject/constants'; // use null address if there is no referrer wallet address
const tx = await mintClubBondContract.sell(tokenAddress, sellAmount, minRefund, referrerWalletAddress);
```


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