added fraction

fraction.js

@@ -0,0 +1,18 @@
+const count_decimal_digits = require("./count_decimal_digits.js");
+
+/**
+ * @private
+ * @param {String} n - decimal string
+ * @returns {Array.<string>} n - fraction like ["123", "100"] (meaning 123/100)
+ */
+function fraction(n) {
+  const decimal_digits = count_decimal_digits(n);
+
+  const numerator = n.replace(/\./g, "").replace(/^0/, "");
+  const denominator = 1 + "0".repeat(decimal_digits);
+
+  return [numerator, denominator];
+}
+
+module.exports = fraction;
+module.exports.default = fraction;