Timestamps, .now( ), and .valueOf ( )

    // datenow.js
    // Date.now( ) vs. date.valueOf( )
    // Jan 1, 1970, 12:00:00
    // number of milliseconds that has passed 
    log = console.log;
    let timestamp1 = Date.now( );	// class method, static method 
    log (timestamp1);
    
    let today = new Date( );	// using the constructor method
    let timestamp2 = today.valueOf( );	// instance method (working on instance of object) 
    log(timestamp2);