请问用JavaScript怎么根据年/周如此:["2017W51","2017W52","2017W53","2018W0

请问用JavaScript怎么根据年/周如此:["2017W51","2017W52","2017W53","2018W01"]来获取这些对应的日期,

var fn=function(y,z){
    var d=new Date();
    d.setFullYear(y);
    d.setMonth(0);
    d.setDate(1);
    for(var i=1;i        d.setDate(d.getDate()+i);
    }
    return d;
}


var arr=["2017W51","2017W52","2017W53","2018W01"];
for(var i=0;i    var ai=arr[i].split(/W/);
    var y=ai[0],z=ai[1];
    console.log(fn(y,z));
}