How to get the amount of token0 and token1 from a Uniswap V3 pool in JS

Question

I have the following functions based on the Uniswap library, but the result of the amounts I get for the two tokens in the pool are different from those shown by Dexscreener. How can I fix this?

const FixedPoint96 = {
  Q96: Big(2).pow(96)
};

function mulDiv(a, b, denominator) {
  return a.mul(b).div(denominator);
}

function getAmount0ForLiquidity(sqrtRatioAX96, sqrtRatioBX96, liquidity) {
  if (sqrtRatioAX96.gt(sqrtRatioBX96)) {
    [sqrtRatioAX96, sqrtRatioBX96] = [sqrtRatioBX96, sqrtRatioAX96];
  }
  const numerator = liquidity.mul(FixedPoint96.Q96).mul(sqrtRatioBX96.sub(sqrtRatioAX96));
  return numerator.div(sqrtRatioBX96).div(sqrtRatioAX96);
}

function getAmount1ForLiquidity(sqrtRatioAX96, sqrtRatioBX96, liquidity) {
  if (sqrtRatioAX96.gt(sqrtRatioBX96)) {
    [sqrtRatioAX96, sqrtRatioBX96] = [sqrtRatioBX96, sqrtRatioAX96];
  }
  return liquidity.mul(sqrtRatioBX96.sub(sqrtRatioAX96)).div(FixedPoint96.Q96);
}

function getAmountsForLiquidity(sqrtRatioX96, sqrtRatioAX96, sqrtRatioBX96, liquidity) {
  let amount0 = Big(0);
  let amount1 = Big(0);

  if (sqrtRatioAX96.gt(sqrtRatioBX96)) {
    [sqrtRatioAX96, sqrtRatioBX96] = [sqrtRatioBX96, sqrtRatioAX96];
  }

  if (sqrtRatioX96.lte(sqrtRatioAX96)) {
    amount0 = getAmount0ForLiquidity(sqrtRatioAX96, sqrtRatioBX96, liquidity);
  } else if (sqrtRatioX96.lt(sqrtRatioBX96)) {
    amount0 = getAmount0ForLiquidity(sqrtRatioX96, sqrtRatioBX96, liquidity);
    amount1 = getAmount1ForLiquidity(sqrtRatioAX96, sqrtRatioX96, liquidity);
  } else {
    amount1 = getAmount1ForLiquidity(sqrtRatioAX96, sqrtRatioBX96, liquidity);
  }

  return [amount0, amount1];
}

async function getPoolBalances(_poolContract, _token0, _token1, _priceInDecimals = false, _print = false) {
  let amounts0 = new Big(0);
  let amounts1 = new Big(0);

  const liquidity = new Big((await _poolContract.liquidity()).toString());
  const MIN_TICK  = -887272;
  const MAX_TICK  =  887272;

  const { sqrtPriceX96 } = await _poolContract.slot0();
  const sqrtPriceCurrent = new Big(sqrtPriceX96.toString());

  const sqrtRatioAX96 = Big(TickMath.getSqrtRatioAtTick(MIN_TICK).toString());
  const sqrtRatioBX96 = Big(TickMath.getSqrtRatioAtTick(MAX_TICK).toString());

  const [amount0, amount1] = getAmountsForLiquidity(sqrtPriceCurrent, sqrtRatioAX96, sqrtRatioBX96, liquidity);

  amounts0 = amount0;
  amounts1 = amount1;

  const decim0 = Big(10).pow(Number(_token0.decimals));
  const decim1 = Big(10).pow(Number(_token1.decimals));

  const balance0 = amounts0.div(decim0);
  const balance1 = amounts1.div(decim1);

  if (_print) {
    const add = await _poolContract.getAddress()
    console.log(
      add.substring(0, 9), "Balance",_token0.symbol, balance0.toString(), "Balance", _token1.symbol, balance1.toString()
    );
  }

  if (_priceInDecimals) {
    return [balance0.toString(), balance1.toString()];
  } else {
    return [amounts0.toString(), amounts1.toString()];
  }
}

Answer 1

You can just query balanceOf(poolAddress) for token0 and token1, that would be much easier.