Count unique elements in array without sorting JavaScript

Let’s say, we have an array of literals that contains some duplicate values −

const arr = ['Cat', 'Dog', 'Cat', 'Elephant', 'Dog', 'Grapes', 'Dog', 'Lion', 'Grapes', 'Lion'];

We are required to write a function that returns the count of unique elements in the array. Will use Array.prototype.reduce() and Array.prototype.lastIndexOf() to do this −

Example

const arr = ['Cat', 'Dog', 'Cat', 'Elephant', 'Dog', 'Grapes', 'Dog',
'Lion', 'Grapes', 'Lion'];
const countUnique = arr => {
   return arr.reduce((acc, val, ind, array) => {
      if(array.lastIndexOf(val) === ind){
         return ++acc;
      };
      return acc;
   }, 0);
};
console.log(countUnique(arr));

Output

The output in the console will be −

5

AmitDiwan

Published on 26-Aug-2020 11:36:52

• Related Questions & Answers
• Sorting array of exactly three unique repeating elements in JavaScript
• Sorting Array Elements in Javascript
• Sorting Array without using sort() in JavaScript
• Unique sort (removing duplicates and sorting an array) in JavaScript
• Counting unique elements in an array in JavaScript
• How to count unique elements in the array using java?
• Fetch Second minimum element from an array without sorting JavaScript
• Sorting array according to increasing frequency of elements in JavaScript
• Sorting array based on increasing frequency of elements in JavaScript
• Check if items in an array are consecutive but WITHOUT SORTING in JavaScript
• JavaScript Count the number of unique elements in an array of objects by an object property?
• Count by unique key in JavaScript
• Sorting elements of stack using JavaScript
• Sorting an array including the elements present in the subarrays in JavaScript
• JavaScript array sorting by level