问JavaScript /节点承诺:按顺序执行它们

EN

var Promise = require("bluebird");
// My Promise enabled function from oReily Safari book
function countdown(seconds, timername) {
    return new Promise(function (resolve, reject) {
        console.log('Countdown : Starting Countdown ' + timername);
        for (let i = seconds; i >= 0; i--) {
            setTimeout(function () {
                if (i > 0)
                    console.log(timername + ' ' + i + '...');
                else
                {
                    console.log('countdown '+timername+' now=='+i+' resolving!');
                    resolve(console.log("Countdown : timename="+timername+" ended"));
                }
            }, (seconds - i) * 1000);
        }
    });
}

/*Basic test of promise */
/* when this is run I expected countdown(5, 'Basic : Timer1') to execute and then when **resolved** THEN countdown(5, "Basic Timer2") to execute. 
 *however what I see is both timers executing at the same time.. 
 */

console.log('Basic : Countdown promise test');
countdown(5, 'Basic : Timer1').
        then(function ()
        {
            /*Success */
            console.log("Basic : Ended Successfully");
        }).
        then(countdown(5, "Basic : Timer2")
                );

Basic : Countdown promise test
Countdown : Starting Countdown Basic : Timer1
Countdown : Starting Countdown Basic : Timer2
Basic : Timer1 5...
Basic : Timer2 5...
Basic : Timer1 4...
Basic : Timer2 4...
Basic : Timer1 3...
Basic : Timer2 3...
Basic : Timer1 2...
Basic : Timer2 2...
Basic : Timer1 1...
Basic : Timer2 1...
countdown Basic : Timer1 now==0 resolving!
Countdown : timename=Basic : Timer1 ended
countdown Basic : Timer2 now==0 resolving!
Countdown : timename=Basic : Timer2 ended
Basic : Ended Successfully
Done.