jwt.js

// First:
//   npm install jsonwebtoken
// https://github.com/auth0/node-jsonwebtoken
//
// Then launch `node` shell.

var jwtLib = require('jsonwebtoken');

var jwtStr = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJjb250ZXh0Ijoic3N2cHpmYWZoZCIsInN1YiI6InVybjpzd2l0Y2hjb25uZXg6dXNlcjo0MCIsImlzcyI6InVybjpzd2l0Y2hjb25uZXg6c3ZjOmF1dGgiLCJleHAiOjE0NzMzNjMxNTMsImlhdCI6MTQ3MzM2Mjg1MywiYXVkIjoidXJuOnN3aXRjaGNvbm5leDpzdmM6bW9iaWxlIn0.tZj08Vlci3g7SYUm-8MxfH_Ty_1rtBGgUzC311-NSaU';

jwt = jwtLib.decode(jwtStr);

if (jwt.exp < Date.now() / 1000) console.log('JWT token is expired.');