为对象数组中的某些属性返回唯一值的函数，按顺序

Question

This is my data

$scope.Reports = [
  { Id: 1, Name: 'Report One', Year: 2016, Month: 5 },
  { Id: 2, Name: 'Report Core', Year: 2016, Month: 5 },
  { Id: 3, Name: 'Report Alpha', Year: 2016, Month: 3 },
  { Id: 4, Name: 'Report Moon', Year: 2015, Month: 5 },
  { Id: 5, Name: 'Report Sky', Year: 2015, Month: 2 }
];

$scope.desc = function (arr) {
            return $('min')
              ($('map')(arr, '-Year'));
        };

I am trying to retrieve the list of the Year values in descending order, so I can use them in an orderBy filter in AngularJs.

So for the data above, I'd want [2016, 2015] .

How can I get that?

Answer 1

I don't know if Angular has something specific to help with this, but in JavaScript it's fairly straight-forward: Determine the unique list of years, then sort them in descending order.

Here's an example doing it by building an object with keys for the years:

 var data = [ { Id: 1, Name: 'Report One', Year: 2016, Month: 5 }, { Id: 2, Name: 'Report Core', Year: 2016, Month: 5 }, { Id: 3, Name: 'Report Alpha', Year: 2016, Month: 3 }, { Id: 4, Name: 'Report Moon', Year: 2015, Month: 5 }, { Id: 5, Name: 'Report Sky', Year: 2015, Month: 2 } ]; var years = getUnique(data, "Year").sort(function(a, b) { // Sorts numerically in descending order return b - a; }); function getUnique(array, prop) { var obj = Object.create(null); array.forEach(function(entry) { obj[entry[prop]] = true; }); return Object.keys(obj); } // Show result document.body.innerHTML = JSON.stringify(years);

I split getUnique off into a function in case you need to reuse it for other similar things.

In an ES2015 environment, you might use set instead of an object (and arrow functions).

Answer 2

在 angular 中使用 loadash。

_.reverse(_.sortedUniq(_.map(a,'Year')))