How to Get Unique Elements in This Array

Get all unique values in a JavaScript array (remove duplicates)

With JavaScript 1.6 / ECMAScript 5 you can use the native filter method of an Array in the following way to get an array with unique values:

function onlyUnique(value, index, self) {
  return self.indexOf(value) === index;
}

// usage example:
var a = ['a', 1, 'a', 2, '1'];
var unique = a.filter(onlyUnique);

console.log(unique); // ['a', 1, 2, '1']

How to get unique values in an array

Since I went on about it in the comments for @Rocket's answer, I may as well provide an example that uses no libraries. This requires two new prototype functions, contains and unique

Array.prototype.contains = function(v) {  for (var i = 0; i < this.length; i++) {    if (this[i] === v) return true;  }  return false;};
Array.prototype.unique = function() {  var arr = [];  for (var i = 0; i < this.length; i++) {    if (!arr.contains(this[i])) {      arr.push(this[i]);    }  }  return arr;}
var duplicates = [1, 3, 4, 2, 1, 2, 3, 8];var uniques = duplicates.unique(); // result = [1,3,4,2,8]
console.log(uniques);

Get unique values from array of arrays

You can use .flat() to flatten your array and then use Set to get its unique values.

Demo:

let arr =   [  [    "s1@example.com",    "s2@example.com"  ],  [    "s1@example.com",    "s3@example.com"  ]]
let arr2 = [...new Set(arr.flat(1))];console.log(arr2)

How to get distinct values from an array of objects in JavaScript?

If this were PHP I'd build an array with the keys and take array_keys at the end, but JS has no such luxury. Instead, try this:

var flags = [], output = [], l = array.length, i;
for( i=0; i<l; i++) {
    if( flags[array[i].age]) continue;
    flags[array[i].age] = true;
    output.push(array[i].age);
}

Fastest way to get ONLY unique values from array?

• The first idea, we can do over two step:

  Step1: Sort the array

  -- There are many algorithms to do it. As I know, currently, the complexity of best algorithm now is O(Nlog(N)) with N is the number of array.

  Step2: Remove the duplicated elements

  -- The complexity of this step is O(N)
  So, over two steps, the complexity is O(N) + O(Nlog(N)). Finally, the complexity is O(Nlog(N))

• The second idea

  This also has the complexity is O(Nlog(N)) but it will be O(N) for next time you want to get the unique age.

  Instead of saving the data in array, you can rebuild in a binary search tree with a little custom. This node in this tree will save all the elements with same age.

  The complexity for the first time you build the tree is O(Nlog(N))

About the algorithm which has the complexity is O(N), currently, I think there are no technique to solve it. :D

How do I get unique elements in this array?

You can just use the method uniq. Assuming your array is ary, call:

ary.uniq{|x| x.user_id}

and this will return a set with unique user_ids.

Get the unique values from two arrays and put them in another array

var array3 = array1.filter(function(obj) { return array2.indexOf(obj) == -1; });

MDN on Array#filter: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/filter

Includes a polyfill for older browsers.

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