Portal fill with mixed decimals

When the token pair has different decimal precison we can end up with a remainder when multiplying by an exchange rate (as one is in 18 decimals and the other is 6 for example)

1 files changed, 4 insertions, 2 deletions

diff --git a/packages/website/ts/components/fill_order.tsx b/packages/website/ts/components/fill_order.tsx
index a6144bd6b..ea94e0987 100644
--- a/packages/website/ts/components/fill_order.tsx
+++ b/packages/website/ts/components/fill_order.tsx
@@ -198,11 +198,13 @@ export class FillOrder extends React.Component<FillOrderProps, FillOrderState> {
             symbol: takerToken.symbol,
         };
         const parsedOrderExpiration = new BigNumber(this.state.parsedOrder.signedOrder.expirationUnixTimestampSec);
-        const exchangeRate = orderMakerAmount.div(orderTakerAmount);
 
         let orderReceiveAmount = 0;
         if (!_.isUndefined(this.props.orderFillAmount)) {
-            const orderReceiveAmountBigNumber = exchangeRate.mul(this.props.orderFillAmount);
+            const orderReceiveAmountBigNumber = orderMakerAmount
+                .times(this.props.orderFillAmount)
+                .dividedBy(orderTakerAmount)
+                .floor();
             orderReceiveAmount = this._formatCurrencyAmount(orderReceiveAmountBigNumber, makerToken.decimals);
         }
         const isUserMaker =