postmanDecodeJWT.js

/**
* This snippet can be used in postman to read the cotnents of a 
* JWT and set a postman variable to the value of one of the claims
*/
let jsonData = pm.response.json();
// use whatever key in the response contains the jwt you want to look into.  This example is using access_token
let jwtContents = jwt_decode(jsonData.access_token);

// Now you can set a postman variable with the value of a claim in the JWT
pm.variable.set("someClaim", jwtContents.payload.someClaim);

function jwt_decode(jwt) {
    var parts = jwt.split('.'); // header, payload, signature
    let tokenContents={};
    tokenContents.header = JSON.parse(atob(parts[0]));
    tokenContents.payload = JSON.parse(atob(parts[1]));
    tokenContents.signature = atob(parts[2]);

    // this just lets you see the jwt contents in the postman console.
    console.log("Token Contents:\n" + JSON.stringify(tokenContents, null, 2));

    return tokenContents;
}