请教一个算法

Question

你是不是希望得到的结果:
{
'2013-8':['title1','title2'],
'2013-9':['title3','title4','title5'],
'2013-10':['title6'],
'2013-11':['title7','title8']
}

Answer 1

var arr = [
 {title:'title1',date:'2013-8-1'},
 {title:'title2',date:'2013-8-23'},
 {title:'title3',date:'2013-9-1'},
 {title:'title4',date:'2013-9-2'},
 {title:'title5',date:'2013-9-3'},
 {title:'title6',date:'2013-10-10'},
 {title:'title7',date:'2013-11-1'},
 {title:'title8',date:'2013-11-2'}
];
var obj = {};
for(var i=0, l = arr.length; i < l; ++i)
{
var d = arr[i].date.match(/\d+-\d+/)[0];
if(obj[d])
obj[d].push(arr[i].title);
else
obj[d] = [arr[i].title];
}
for(var i in obj)
document.write(i+":"+obj[i]+"<br />");