[new feature] add CountDown component (#3805)

src/utils/format/string.ts

@@ -4,6 +4,12 @@ export function camelize(str: string): string {
   return str.replace(camelizeRE, (_, c) => c.toUpperCase());
 }
 
-export function padZero(num: number | string): string {
-  return (num < 10 ? '0' : '') + num;
+export function padZero(num: number | string, targetLength = 2): string {
+  let str = num + '';
+
+  while (str.length < targetLength) {
+    str = '0' + str;
+  }
+
+  return str;
 }