Add 'yy' format (#61)

* Add 'yy' format

* Fix 'yy' parsing

---------

Co-authored-by: Kasper <[email protected]>

Author: erezarnon

src/lib/parse.ts

@@ -57,6 +57,9 @@ export function parse(str: string, tokens: FormatToken[], baseDate: Date | null)
   function parseToken(token: FormatToken) {
     if (typeof token === 'string') {
       parseString(token)
+    } else if (token.id === 'yy') {
+      const value = parseUint(/^[0-9]{2}/, 0, 99)
+      if (value !== null) year = 2000 + value
     } else if (token.id === 'yyyy') {
       const value = parseUint(/^[0-9]{4}/, 0, 9999)
       if (value !== null) year = value
@@ -103,6 +106,10 @@ const ruleTokens: RuleToken[] = [
     id: 'yyyy',
     toString: (d: Date) => d.getFullYear().toString(),
   },
+  {
+    id: 'yy',
+    toString: (d: Date) => d.getFullYear().toString().slice(-2),
+  },
   {
     id: 'MM',
     toString: (d: Date) => twoDigit(d.getMonth() + 1),

src/routes/docs/+page.md

@@ -50,6 +50,7 @@ Example format string: `yyyy-MM-dd HH:mm:ss`
 | Pattern | Result example |
 | :------ | :------------- |
 | `yyyy`  | 2021           |
+| `yy`    | 21             |
 | `MM`    | 12             |
 | `dd`    | 31             |
 | `HH`    | 23             |