A function that can retrieve distinct values for a specific property within an array of objects while maintaining their original order

Question

A function that can retrieve distinct values for a specific property within an array of objects while maintaining their original order

Here is some information I have:

$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 attempting to extract the list of Year values in descending order, which will be used with an orderBy filter in AngularJs.

Given the above data, I wish to obtain [2016, 2015].

Can anyone guide me on how to achieve this?

javascript arrays angularjs

Answer 1

Answer №1

While I'm not sure about any specific Angular features for this task, in JavaScript, it's quite simple: First, find the distinct years and then arrange them in descending order.

Here is an example that accomplishes this by creating an object with year keys:

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 = retrieveUnique(data, "Year").sort(function(a, b) {
  // Numerically sorts in descending order
  return b - a;
});

function retrieveUnique(array, prop) {
  var obj = Object.create(null);
  array.forEach(function(entry) {
    obj[entry[prop]] = true;
  });
  return Object.keys(obj);
}

// Displaying the result
document.body.innerHTML = JSON.stringify(years);

I extracted the retrieveUnique function in case you need to apply it to similar scenarios.

In an ES2015 setting, you might opt for using a set instead of an object (and arrow functions).

Answer 2

While I'm not sure about any specific Angular features for this task, in JavaScript, it's quite simple: First, find the distinct years and then arrange them in descending order.

Here is an example that accomplishes this by creating an object with year keys:

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 = retrieveUnique(data, "Year").sort(function(a, b) {
  // Numerically sorts in descending order
  return b - a;
});

function retrieveUnique(array, prop) {
  var obj = Object.create(null);
  array.forEach(function(entry) {
    obj[entry[prop]] = true;
  });
  return Object.keys(obj);
}

// Displaying the result
document.body.innerHTML = JSON.stringify(years);

I extracted the retrieveUnique function in case you need to apply it to similar scenarios.

In an ES2015 setting, you might opt for using a set instead of an object (and arrow functions).

Answer 3

Answer №2

Learn how to utilize loadash with Angular framework.

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

Answer 4

Learn how to utilize loadash with Angular framework.

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

A function that can retrieve distinct values for a specific property within an array of objects while maintaining their original order

Answer №1

Answer №2

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