Erro router front

backend.js:6 ReferenceError: router is not defined
    at Page.js:22
    at hs (react-dom.production.min.js:198)
    at xu (react-dom.production.min.js:255)
    at t.unstable_runWithPriority (scheduler.production.min.js:18)
    at qo (react-dom.production.min.js:120)
    at wu (react-dom.production.min.js:254)
    at react-dom.production.min.js:254
    at z (scheduler.production.min.js:17)
    at MessagePort.O.port1.onmessage (scheduler.production.min.js:14)
r @ backend.js:6
fs @ react-dom.production.min.js:196
Os.n.callback @ react-dom.production.min.js:210
_i @ react-dom.production.min.js:131
bi @ react-dom.production.min.js:131
bu @ react-dom.production.min.js:252
t.unstable_runWithPriority @ scheduler.production.min.js:18
qo @ react-dom.production.min.js:120
yu @ react-dom.production.min.js:244
iu @ react-dom.production.min.js:223
(anonymous) @ react-dom.production.min.js:121
t.unstable_runWithPriority @ scheduler.production.min.js:18
qo @ react-dom.production.min.js:120
Go @ react-dom.production.min.js:121
$o @ react-dom.production.min.js:120
xu @ react-dom.production.min.js:255
t.unstable_runWithPriority @ scheduler.production.min.js:18
qo @ react-dom.production.min.js:120
wu @ react-dom.production.min.js:254
(anonymous) @ react-dom.production.min.js:254
z @ scheduler.production.min.js:17
O.port1.onmessage @ scheduler.production.min.js:14
scheduler.production.min.js:14 Uncaught ReferenceError: router is not defined
    at Page.js:22
    at hs (react-dom.production.min.js:198)
    at xu (react-dom.production.min.js:255)
    at t.unstable_runWithPriority (scheduler.production.min.js:18)
    at qo (react-dom.production.min.js:120)
    at wu (react-dom.production.min.js:254)
    at react-dom.production.min.js:254
    at z (scheduler.production.min.js:17)
    at MessagePort.O.port1.onmessage (scheduler.production.min.js:14)
(anonymous) @ Page.js:22
hs @ react-dom.production.min.js:198
xu @ react-dom.production.min.js:255
t.unstable_runWithPriority @ scheduler.production.min.js:18
qo @ react-dom.production.min.js:120
wu @ react-dom.production.min.js:254
(anonymous) @ react-dom.production.min.js:254
z @ scheduler.production.min.js:17
O.port1.onmessage @ scheduler.production.min.js:14