Rewrite frontend using create-react-app

client/NumberUtils.js

@@ -0,0 +1,15 @@
+export const formatNumber = (n) => {
+  const digits = String(n).split('')
+  const groups = []
+
+  while (digits.length)
+    groups.unshift(digits.splice(-3).join(''))
+
+  return groups.join(',')
+}
+
+export const parseNumber = (s) =>
+  parseInt(s.replace(/,/g, ''), 10) || 0
+
+export const formatPercent = (n, fixed = 1) =>
+  String((n.toPrecision(2) * 100).toFixed(fixed))