var startTime = new Date().getTime();
var count = 0;
//耗時任務
setInterval(function(){
var i = 0;
while(i++ < 100000000);
}, 0);
setInterval(function(){
count++;
console.log(new Date().getTime() - (startTime + count * 1000));
}, 1000);

176
340
495
652
807
961
1114
1268
1425
1579
1734
1888
2048
2201
2357
2521
2679
2834
2996
......

var startTime = new Date().getTime();
var count = 0;
setInterval(function(){
var i = 0;
while(i++ < 100000000);
}, 0);
function fixed() {
count++;
var offset = new Date().getTime() - (startTime + count * 1000);
var nextTime = 1000 - offset;
if (nextTime < 0) nextTime = 0;
setTimeout(fixed, nextTime);

console.log(new Date().getTime() - (startTime + count * 1000));
}
setTimeout(fixed, 1000);

186
200
230
271
158
899
900
899
900
899
899
899
902
899
418
202
232
266
145
174
192
214
242
268
149
179
214
......