2 files changed, 32 insertions, 5 deletions
diff --git a/packages/instant/src/containers/selected_erc20_asset_amount_input.ts b/packages/instant/src/containers/selected_erc20_asset_amount_input.ts
index 3d0895aac..1fc5b6d8c 100644
--- a/packages/instant/src/containers/selected_erc20_asset_amount_input.ts
+++ b/packages/instant/src/containers/selected_erc20_asset_amount_input.ts
@@ -13,6 +13,7 @@ import { State } from '../redux/reducer';
 import { ColorOption } from '../style/theme';
 import { ERC20Asset, OrderProcessState, ZeroExInstantError } from '../types';
 import { getBestAddress } from '../util/address';
+import { balanceUtil } from '../util/balance';
 import { BigNumberInput } from '../util/big_number_input';
 import { errorUtil } from '../util/error';
 import { web3Wrapper } from '../util/web3_wrapper';
@@ -81,11 +82,7 @@ const updateBuyQuoteAsync = async (
 
     // set error if user doesn't have appropriate balance
     const takerAddress = await getBestAddress();
-    const balanceWei = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-    if (balanceWei < newBuyQuote.worstCaseQuoteInfo.totalEthAmount) {
-        const balanceError = new Error(ZeroExInstantError.InsufficientBalance);
-        errorUtil.errorFlasher.flashNewError(dispatch, balanceError);
-    }
+    await balanceUtil.checkSufficientBalanceAndFlashError(takerAddress, newBuyQuote, web3Wrapper, dispatch);
 };
 
 const debouncedUpdateBuyQuoteAsync = _.debounce(updateBuyQuoteAsync, 200, { trailing: true });
diff --git a/packages/instant/src/util/balance.ts b/packages/instant/src/util/balance.ts
new file mode 100644
index 000000000..d442da9e0
--- /dev/null
+++ b/packages/instant/src/util/balance.ts
@@ -0,0 +1,30 @@
+import { BuyQuote } from '@0x/asset-buyer';
+import { Web3Wrapper } from '@0x/web3-wrapper';
+import { Dispatch } from 'redux';
+
+import { ZeroExInstantError } from '../types';
+
+import { errorUtil } from './error';
+
+export const balanceUtil = {
+    /**
+     * Checks to see if user has enough balance to buy assets
+     * If they do not, flash an error and return false
+     * If they do, return true
+     */
+    checkSufficientBalanceAndFlashError: async (
+        takerAddress: string,
+        buyQuote: BuyQuote,
+        web3Wrapper: Web3Wrapper,
+        dispatch: Dispatch,
+    ) => {
+        const balanceWei = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+
+        if (balanceWei < buyQuote.worstCaseQuoteInfo.totalEthAmount) {
+            const balanceError = new Error(ZeroExInstantError.InsufficientBalance);
+            errorUtil.errorFlasher.flashNewError(dispatch, balanceError);
+            return false;
+        }
+        return true;
+    },
+};