1 files changed, 29 insertions, 0 deletions
diff --git a/packages/instant/src/util/big_number_input.ts b/packages/instant/src/util/big_number_input.ts
new file mode 100644
index 000000000..d2a9a8dc5
--- /dev/null
+++ b/packages/instant/src/util/big_number_input.ts
@@ -0,0 +1,29 @@
+import { BigNumber } from '@0x/utils';
+import * as _ from 'lodash';
+
+/**
+ *  A BigNumber extension that is more flexible about decimal strings.
+ *  Such as allowing:
+ *  new BigNumberInput('0.') => 0
+ *  new BigNumberInput('1.') => 1
+ *  new BigNumberInput('1..') => still throws
+ */
+export class BigNumberInput extends BigNumber {
+    private readonly _isEndingWithDecimal: boolean;
+    constructor(bigNumberString: string) {
+        const hasDecimalPeriod = _.endsWith(bigNumberString, '.');
+        let internalString = bigNumberString;
+        if (hasDecimalPeriod) {
+            internalString = bigNumberString.slice(0, -1);
+        }
+        super(internalString);
+        this._isEndingWithDecimal = hasDecimalPeriod;
+    }
+    public toDisplayString(): string {
+        const internalString = super.toString();
+        if (this._isEndingWithDecimal) {
+            return `${internalString}.`;
+        }
+        return internalString;
+    }
+}