feat: 完成....

tonesc-red-packet/lib/currency.ts

@@ -0,0 +1,15 @@
+/**
+ * 从最小单位（step）中推导小数位数
+ *
+ * "1.00000000"   -> 0
+ * "0.01000000"   -> 2
+ * "0.00010000"   -> 4
+ */
+export function getDecimalPlacesFromStep(step: string): number {
+    const [, decimal = ""] = step.split(".")
+
+    if (!decimal) return 0
+
+    const index = decimal.search(/[1-9]/)
+    return index === -1 ? 0 : index + 1
+}