JWT deoded in Typescript gives the error "Object is possibly 'undefined"

Question

I am trying to decode the JWT token in order to check wheather is it valid or not. But I am getting the error that the decoded object is possibly 'undefined'

import jwt_decode, { JwtPayload } from "jwt-decode";
    if (token) {
      const decoded = jwt_decode<JwtPayload>(token || "") || null;

      if (decoded) {
        const currentTime = Date.now() / 1000;
        if (decoded?.exp < currentTime) {  //Object is possibly 'undefined'.
          dispatch(logout());
          localStorage.removeItem("token");
          setLoading(false);
        }
      }
}

Could you show the `JwtPayload` type definition ? I have reasons to believe it comes from here — nook, Sep 21 '22 at 15:13
@nook I have updated the question, jwtpayload comes from the library jwt-decode — Illyrian, Sep 21 '22 at 15:41

score 4 · Accepted Answer · answered Sep 21 '22 at 16:05

4

decoded.exp is possibly undefined, so you have to check it first before comparing it to currentTime

if (decoded?.exp && decoded.exp < currentTime) { }

answered Sep 21 '22 at 16:05

axtck

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the `?` in `decoded?.exp < currentTime` already does that. It can end up comparing `undefined < currentTime` instead but that's not a problem either because that's always `false` – zapl Sep 21 '22 at 16:11
@zapl exp is possibly undefined too, it does seem to fix the compilation error try it out here https://www.typescriptlang.org/play?ssl=7&ssc=2&pln=1&pc=1#code/MYewdgzgLgBAJgU1IuAuGBXMiBmBLMBOGAHxgG8YEAPAB3TAwFsAjBAJ1M2wX0OIC+MALwUqddFlwEiMAQG4AUIrw4YACkTIiASgqKYMUJFjAM7dgjBQAKniYIRMACIBDKAgB0YEAHd1egD0MACMAAwRSoaqGlogKJ40tDAAZCnwSPFEAPyJdDAAPEbmltZ2DnqUMAZyigJAA – axtck Sep 21 '22 at 16:18
2

oops, right, `strictNullChecks` doesn't like undefined < number – zapl Sep 21 '22 at 16:22

JWT deoded in Typescript gives the error "Object is possibly 'undefined"

1 Answers1