Very simple helper class to decode JWT token on javscript

JWTHelper.js

"use strict";
export class JWTHelper {

    /**
     * Decode a JWT token
     * 
     * @static
     * @param {string} token
     * @throws Error 
     * @returns object|boolean
     * @memberof JWTHelper
     */
    static decode(token) {
        if (!token || token === '') {
            throw new Error("Token is empty");
        }

        const tokenParts = token.split('.');

        // This token is invalid
        if (tokenParts.length < 3) {
            throw new Error("Token is invalid");
        }

        // 0 - header
        // 1 - payload
        // 2 - signature
        // Decode from base64 to json string
        let [header, payload, signature] = tokenParts
            .map(parts => new Buffer(parts, 'base64').toString());

        // convert the json string to object
        // this will throw error if fail on parsing
        // but we dont wrap into try/catch, so the user
        // could catch it themself 
        header = JSON.parse(header);
        payload = JSON.parse(payload);

        return {
            header,
            payload,
            signature
        };
    }
    
    
    /**
     * Checks if the token has expired
     * 
     * @static
     * @param {string} token
     * @throws Error 
     * @returns boolean
     * @memberof JWTHelper
     */
    static hasTokenExpired(token) {
        const decodedToken = this.decode(token);
        const payload = decodedToken.payload;
        /*
        Payload
        {
            "iat": timestamp,
            "exp": timestamp
        }
        */
        if (payload.hasOwnProperty("exp")) {
            const currentTime = new Date().getTime();
            const expTime = new Date(payload.exp * 1000).getTime();
            return (currentTime > expTime)
        }
        
        return false;
    }    
}