var year = 2012;
var week = 2;
var d = new Date("Jan 01," + year + " 01:00:00");
var w = d.getTime() + 604800000 * (week - 1);
var n1 = new Date(w);
var n2 = new Date(w + 518400000)

console.log(n1);
console.log(n2);

n1包含一周的第一天
n2包含一周的最后一天@H_502_3@

至于常数：604800000是一周,以毫秒为单位518400000是六天@H_502_3@