feat: 前端

frontend/src/utils/jwt.ts

@@ -0,0 +1,28 @@
+export type JwtPayload = {
+  account_id?: number
+  username?: string
+  exp?: number
+  iat?: number
+  nbf?: number
+  [key: string]: unknown
+}
+
+function base64UrlToBase64(input: string) {
+  const base64 = input.replace(/-/g, '+').replace(/_/g, '/')
+  const pad = base64.length % 4
+  return pad === 0 ? base64 : base64 + '='.repeat(4 - pad)
+}
+
+export function decodeJwtPayload(token: string): JwtPayload | null {
+  const [, payload] = token.split('.')
+  if (!payload) return null
+
+  try {
+    const json = atob(base64UrlToBase64(payload))
+    const parsed = JSON.parse(json)
+    if (!parsed || typeof parsed !== 'object') return null
+    return parsed as JwtPayload
+  } catch {
+    return null
+  }
+}