Sorting news items by their associated date - Javascript

Question

I've been trying to solve this for a while with no success. I have 2 arrays:

var dates = [
    new Date(2014, 4, 11, 10, 10, 0).getTime(),
    new Date(2012, 4, 10, 8, 20, 0).getTime(),
    new Date(2013, 4, 9, 7, 20, 0).getTime(),
    new Date(2010, 4, 7, 12, 59, 0).getTime()
            ];

var newsItems = ["NewsItem1","NewsItem2","NewsItem3","NewsItem4"];

I'm using the function var desc = dates.sort(function(a,b){return b-a}); To sort the date array, however, I haven't been able to figure out how to also rearrange the newsItems array to align it with the dates array. I tried this but it doesn't seem to work:

var datesDuplicate = [
    new Date(2014, 4, 11, 10, 10, 0).getTime(),
    new Date(2012, 4, 10, 8, 20, 0).getTime(),
    new Date(2013, 4, 9, 7, 20, 0).getTime(),
    new Date(2010, 4, 7, 12, 59, 0).getTime()
            ];
for(var i = 0; i < arrayLength; i++){
    for(var j = 0; j < arrayLength; j++){
        if(dates[i] == datesDuplicate[j]){
            document.getElementById(getElement(i)).innerHTML = newsItems[j];
            break;
        }
    }

}

Any help is highly appreciated.

Answer 1

If you want the news items and dates to be associated to each other they should be part of the same object.

 var items = [
   { date: new Date(2014, 4, 11, 10, 10, 0).getTime(), label: "NewsItem1" },
   { date: new Date(2012, 4, 10, 8, 20, 0).getTime(), label: "NewsItem2" },
   etc...
 ];

and then you can sort it like

 var desc = items.sort(function(a,b){return b.date-a.date});

Answer 2

try something like this

var news = [
   {date: new Date(2014, 4, 11, 10, 10, 0).getTime(), item: "NewsItem1" },
   {date: new Date(2012, 4, 10, 8, 20, 0).getTime(), item: "..." },
   {date: new Date(2013, 4, 9, 7, 20, 0).getTime(), item: "..." },
   {...}
];

You'll need to tweak your sort function, too. If you have to convert from two arrays, try combining them into the above structure with a zip.

Answer 3

Your abstraction could be improved by pairing dates with newsItems:

var datePairs = 
[
  ["NewsItem1", new Date(2014, 4, 11, 10, 10, 0).getTime()],
  ["NewsItem2", new Date(2012, 4, 10, 8, 20, 0).getTime()],
  ["NewsItem3", new Date(2013, 4, 9, 7, 20, 0).getTime()],
];

var desc = datePairs.sort(function(a,b){return b[1]-a[1]}); //sort by date (the second element of each element)

Answer 4

If you didn't have any control over how the data is structured and were stuck with the 2 arrays (which were dense and had the same length), then using ECMA5 methods you could sort them like this.

Javascript

var dates = [
        new Date(2014, 4, 11, 10, 10, 0).getTime(),
        new Date(2012, 4, 10, 8, 20, 0).getTime(),
        new Date(2013, 4, 9, 7, 20, 0).getTime(),
        new Date(2010, 4, 7, 12, 59, 0).getTime()
    ],
    newsItems = ["NewsItem1", "NewsItem2", "NewsItem3", "NewsItem4"];

dates.map((function (date, index) {
    return {
        date: date,
        item: this[index]
    };
}), newsItems).sort(function (a, b) {
    return b.date - a.date;
}).forEach(function (record, index) {
    dates[index] = record.date;
    newsItems[index] = record.item
});

console.log(dates, newsItems);

Output

[1399795800000, 1368076800000, 1336630800000, 1273229940000] ["NewsItem1", "NewsItem3", "NewsItem2", "NewsItem4"] 

On jsFiddle